[FIX] account: Cash rounding

Steps to reproduce:
- Enable Automated Valuation.
- Set the cost of Acoustic Bloc Screens to 287.33.
- Set the Product Category on the product to have AVCO automated valuation.
- Enable Cash Rounding.
- Create a Cash Rounding (see tests).
- Make an invoice selling one Acoustic Bloc Screen and remove the tax.
- Set the Cash Rounding on the invoice under "Other Info".
- Confirm the invoice.

Bug:
when summing the ammount of all the lines the result is slightly off
(float accuracy) this will create an unnecessary cash rounding to
compensate

Fix:
round the sum to the currency precision before checking for the cash rounding

opw-3681307

closes odoo/odoo#152112

X-original-commit: 4a6ec1a667ee3d2fba00d277b4c7e8a730a45ecd
Signed-off-by: Walid Hanniche (waha) <waha@odoo.com>

addons/account/models/account_cash_rounding.py

@@ -61,5 +61,6 @@ class AccountCashRounding(models.Model):
         :param amount: The amount
         :return: round(difference)
         """
+        amount = currency.round(amount)
         difference = self.round(amount) - amount
         return currency.round(difference)

addons/account/tests/test_account_move_in_invoice.py

@@ -758,6 +758,38 @@ class TestAccountMoveInInvoiceOnchanges(AccountTestInvoicingCommon):
             'amount_total': 1384.0,
         })
 
+    def test_compute_cash_rounding_lines(self):
+        cash_rounding_add_invoice_line = self.env['account.cash.rounding'].create({
+            'name': 'Add invoice line Rounding Down',
+            'rounding': .1,
+            'strategy': 'add_invoice_line',
+            'profit_account_id': self.company_data['default_account_revenue'].id,
+            'loss_account_id': self.company_data['default_account_expense'].id,
+            'rounding_method': 'DOWN',
+        })
+        move = self.env['account.move'].create({
+            'move_type': 'in_invoice',
+            'partner_id': self.partner_a.id,
+            'invoice_date': '2019-01-01',
+            'invoice_cash_rounding_id': cash_rounding_add_invoice_line.id,
+            'invoice_line_ids': [
+                Command.create({
+                    'name': 'line',
+                    'price_unit': 295,
+                    'tax_ids': [],
+                }),
+                Command.create({
+                    'name': 'cost',
+                    'price_unit': 280.33,
+                }),
+                Command.create({
+                    'name': 'cost neg',
+                    'price_unit': -280.33,
+                }),
+            ],
+        })
+        self.assertFalse(move.line_ids.filtered(lambda line: line.display_type == 'rounding'))
+
     def test_in_invoice_line_onchange_cash_rounding_1(self):
         # Required for `invoice_cash_rounding_id` to be visible in the view
         self.env.user.groups_id += self.env.ref('account.group_cash_rounding')