Add round_price

We add a common method to round prices that are stored using the price digits.
It is useless to use the digits from the field because it can not be changed in
any other way than by configuration.

issue9146
review299521002

commission.py

@@ -20,7 +20,7 @@ from trytond.pool import Pool
 from trytond.wizard import Wizard, StateView, StateAction, Button
 from trytond.transaction import Transaction
 
-from trytond.modules.product import price_digits
+from trytond.modules.product import price_digits, round_price
 
 from .exceptions import FormulaError
 
@@ -122,14 +122,12 @@ class Agent(ModelSQL, ModelView):
                 group_by=commission.agent)
             cursor.execute(*query)
             amounts.update(dict(cursor.fetchall()))
-        digits = cls.pending_amount.digits
-        exp = Decimal(str(10.0 ** -digits[1]))
         for agent_id, amount in amounts.items():
             if amount:
                 # SQLite uses float for SUM
                 if not isinstance(amount, Decimal):
                     amount = Decimal(str(amount))
-                amounts[agent_id] = amount.quantize(exp)
+                amounts[agent_id] = round_price(amount)
         return amounts
 
     @property

invoice.py

@@ -1,14 +1,13 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
-
-from decimal import Decimal
-
 from trytond.pool import PoolMeta, Pool
 from trytond.model import ModelView, Workflow, fields
 from trytond.pyson import Eval, If, Bool
 from trytond.transaction import Transaction
 from trytond.tools import grouped_slice
 
+from trytond.modules.product import round_price
+
 
 class Invoice(metaclass=PoolMeta):
     __name__ = 'account.invoice'
@@ -156,8 +155,7 @@ class InvoiceLine(metaclass=PoolMeta):
                     self.amount, agent.currency, round=False)
             amount = self._get_commission_amount(amount, plan)
             if amount:
-                digits = Commission.amount.digits
-                amount = amount.quantize(Decimal(str(10.0 ** -digits[1])))
+                amount = round_price(amount)
             if not amount:
                 continue