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

stock.py

@@ -8,7 +8,7 @@ from trytond.pyson import Eval, Bool
 from trytond.pool import Pool, PoolMeta
 from trytond.transaction import Transaction
 
-from trytond.modules.product import price_digits
+from trytond.modules.product import price_digits, round_price
 
 
 class ShipmentIn(metaclass=PoolMeta):
@@ -91,8 +91,8 @@ class ShipmentIn(metaclass=PoolMeta):
                 move_cost = cost / Decimal(len(moves))
             else:
                 move_cost = cost * quantity * unit_prices[move.id] / sum_value
-            unit_shipment_cost = (move_cost / quantity).quantize(exp,
-                rounding=ROUND_DOWN)
+            unit_shipment_cost = round_price(
+                move_cost / quantity, rounding=ROUND_DOWN)
             costs.append({
                     'unit_shipment_cost': unit_shipment_cost,
                     'difference': move_cost - (unit_shipment_cost * quantity),
@@ -114,8 +114,8 @@ class ShipmentIn(metaclass=PoolMeta):
             unit_shipment_cost = Currency.compute(
                 self.company.currency, cost['unit_shipment_cost'],
                 move.currency, round=False)
-            unit_shipment_cost = unit_shipment_cost.quantize(
-                exp, rounding=ROUND_HALF_EVEN)
+            unit_shipment_cost = round_price(
+                unit_shipment_cost, rounding=ROUND_HALF_EVEN)
             move.unit_price += unit_shipment_cost
             move.unit_shipment_cost = unit_shipment_cost
         Move.save(moves)

tryton.cfg

@@ -4,6 +4,7 @@ depends:
     carrier
     currency
     ir
+    product
     res
     stock
 extras_depend: