[FIX] point_of_sale: return with rounding < 0.01

- Set the currency to a rounding of 0.001
- Create a POS order:
  Unit Price: 0.12
  Quantity: 0.1
- Pay and validate
- From the backend, return the products on the create order
- Click on 'Payment'

The proposed amount is 0.01, not 0.012. It is not possible to complete
the payment process since the field is rounded at DB level to 2 digits
of precision.

We make consistent the `amount` field with the various amounts on the
`pos.order`. By using a `digits=0` and forcing the rounding, we avoid
inconsistent rounding between the order and the payment.

opw-1864344

addons/point_of_sale/wizard/pos_payment.py

@@ -2,6 +2,7 @@
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
 from odoo import api, fields, models, _
+from odoo.tools import float_is_zero
 
 
 class PosMakePayment(models.TransientModel):
@@ -30,7 +31,7 @@ class PosMakePayment(models.TransientModel):
 
     session_id = fields.Many2one('pos.session', required=True, default=_default_session)
     journal_id = fields.Many2one('account.journal', string='Payment Mode', required=True, default=_default_journal)
-    amount = fields.Float(digits=(16, 2), required=True, default=_default_amount)
+    amount = fields.Float(digits=0, required=True, default=_default_amount)
     payment_name = fields.Char(string='Payment Reference')
     payment_date = fields.Date(string='Payment Date', required=True, default=lambda *a: fields.Datetime.now())
 
@@ -49,11 +50,13 @@ class PosMakePayment(models.TransientModel):
         """
         self.ensure_one()
         order = self.env['pos.order'].browse(self.env.context.get('active_id', False))
+        currency = order.pricelist_id.currency_id
         amount = order.amount_total - order.amount_paid
         data = self.read()[0]
         # add_payment expect a journal key
         data['journal'] = data['journal_id'][0]
-        if amount != 0.0:
+        data['amount'] = currency.round(data['amount']) if currency else data['amount']
+        if not float_is_zero(amount, precision_rounding=currency.rounding or 0.01):
             order.add_payment(data)
         if order.test_paid():
             order.action_pos_order_paid()