diff --git a/addons/point_of_sale/point_of_sale.py b/addons/point_of_sale/point_of_sale.py
index 370e150295d..6eb63c79089 100644
--- a/addons/point_of_sale/point_of_sale.py
+++ b/addons/point_of_sale/point_of_sale.py
@@ -1506,6 +1506,22 @@ class pos_order_line(osv.osv):
             line[2]['tax_ids'] = [(6, 0, [x.id for x in product.taxes_id])]
         return line
 
+    @api.onchange('product_id')
+    def _onchange_product_id(self):
+        if not self.product_id:
+            return
+        if not self.order_id.pricelist_id:
+           raise UserError(
+               _('You have to select a pricelist in the sale form !\n' \
+               'Please set one before choosing a product.'))
+
+        self.tax_ids = self.product_id.taxes_id.filtered(lambda r: not self.company_id or r.company_id == self.company_id)
+        fpos = self.order_id.fiscal_position_id
+        tax_ids_after_fiscal_position = fpos.map_tax(self.tax_ids) if fpos else self.tax_ids
+        price = self.order_id.pricelist_id.price_get(
+            self.product_id.id, self.qty or 1.0, self.order_id.partner_id.id)[self.order_id.pricelist_id.id]
+        self.price_unit = self.env['account.tax']._fix_tax_included_price(price, self.product_id.taxes_id, tax_ids_after_fiscal_position)
+
     def onchange_product_id(self, cr, uid, ids, pricelist, product_id, qty=0, partner_id=False, context=None):
         context = context or {}
         if not product_id:
@@ -1597,20 +1613,14 @@ class pos_order_line(osv.osv):
     @api.depends('price_unit', 'tax_ids', 'qty', 'discount', 'product_id')
     def _compute_amount_line_all(self):
         for line in self:
-            currency = line.order_id.pricelist_id.currency_id
-            taxes = line.tax_ids.filtered(lambda tax: tax.company_id.id == line.order_id.company_id.id)
-            fiscal_position_id = line.order_id.fiscal_position_id
-            if fiscal_position_id:
-                taxes = fiscal_position_id.map_tax(taxes)
+            fpos = line.order_id.fiscal_position_id
+            tax_ids_after_fiscal_position = fpos.map_tax(line.tax_ids) if fpos else line.tax_ids
             price = line.price_unit * (1 - (line.discount or 0.0) / 100.0)
-            line.price_subtotal = line.price_subtotal_incl = price * line.qty
-            if taxes:
-                taxes = taxes.compute_all(price, currency, line.qty, product=line.product_id, partner=line.order_id.partner_id or False)
-                line.price_subtotal = taxes['total_excluded']
-                line.price_subtotal_incl = taxes['total_included']
-
-            line.price_subtotal = currency.round(line.price_subtotal)
-            line.price_subtotal_incl = currency.round(line.price_subtotal_incl)
+            taxes = tax_ids_after_fiscal_position.compute_all(price, line.order_id.pricelist_id.currency_id, line.qty, product=line.product_id, partner=line.order_id.partner_id)
+            line.update({
+                'price_subtotal_incl': taxes['total_included'],
+                'price_subtotal': taxes['total_excluded'],
+            })
 
     # DEPRECATED, REMOVE ME IN v10
     def _amount_line_all(self, cr, uid, ids, field_names, arg, context=None):
diff --git a/addons/point_of_sale/point_of_sale_view.xml b/addons/point_of_sale/point_of_sale_view.xml
index c3e20ee40b1..4450111e5af 100644
--- a/addons/point_of_sale/point_of_sale_view.xml
+++ b/addons/point_of_sale/point_of_sale_view.xml
@@ -35,10 +35,10 @@
                         <page string="Products">
                             <field name="lines" colspan="4" nolabel="1">
                                 <tree string="Order lines" editable="bottom">
-                                    <field name="product_id" on_change="onchange_product_id(parent.pricelist_id,product_id,qty,parent.partner_id)"/>
-                                    <field name="qty" on_change="onchange_qty(parent.pricelist_id,product_id, discount, qty, price_unit, context)"/>
-                                    <field name="price_unit" on_change="onchange_qty(parent.pricelist_id,product_id, discount, qty, price_unit, context)" widget="monetary"/>
-                                    <field name="discount"  on_change="onchange_qty(parent.pricelist_id,product_id, discount, qty, price_unit, context)" widget="monetary"/>
+                                    <field name="product_id"/>
+                                    <field name="qty"/>
+                                    <field name="price_unit" widget="monetary"/>
+                                    <field name="discount" widget="monetary"/>
                                     <field name="tax_ids_after_fiscal_position" widget="many2many_tags"/>
                                     <field name="tax_ids" widget="many2many_tags" invisible="1"/>
                                     <field name="price_subtotal" widget="monetary"/>
@@ -46,10 +46,10 @@
                                 </tree>
                                 <form string="Order lines">
                                     <group col="4">
-                                        <field name="product_id" on_change="onchange_product_id(parent.pricelist_id,product_id,qty,parent.partner_id)"/>
-                                        <field name="qty" on_change="onchange_qty(parent.pricelist_id,product_id, discount, qty, price_unit, context)"/>
-                                        <field name="discount"  on_change="onchange_qty(parent.pricelist_id,product_id, discount, qty, price_unit, context)" widget="monetary"/>
-                                        <field name="price_unit" on_change="onchange_qty(parent.pricelist_id,product_id, discount, qty, price_unit, context)" widget="monetary"/>
+                                        <field name="product_id"/>
+                                        <field name="qty"/>
+                                        <field name="discount" widget="monetary"/>
+                                        <field name="price_unit" widget="monetary"/>
                                         <field name="price_subtotal" invisible="1" widget="monetary"/>
                                         <field name="price_subtotal_incl" invisible="1" widget="monetary"/>
                                         <field name="tax_ids_after_fiscal_position" widget="many2many_tags"/>