diff -r fdfe606e6b87 stock.py
--- a/trytond/trytond/modules/stock_lot/stock.py	Thu Feb 19 00:04:21 2015 +0100
+++ b/trytond/trytond/modules/stock_lot/stock.py	Mon Oct 05 11:56:24 2015 +0200
@@ -119,16 +119,19 @@
                         round=False)
                     if quantity < out_quantity:
                         outgoing_moves.extend(Move.copy([out_move], default={
-                                    'quantity': out_quantity - quantity,
+                                    'quantity': Uom.round(
+                                        out_quantity - quantity,
+                                        out_move.uom.rounding),
                                     }))
                         Move.write([out_move], {
-                                'quantity': quantity,
+                                'quantity': Uom.round(
+                                        quantity, out_move.uom.rounding),
                                 })
                     Move.write([out_move], {
                             'lot': move.lot.id,
                             })
                     quantity -= out_quantity
-                assert quantity <= 0
+                assert quantity <= move.product.default_uom.rounding
 
 
 class ShipmentOutReturn:
diff -r 519c1c1a1ca2 shipment.py
--- a/trytond/trytond/modules/stock/shipment.py	Mon Oct 05 12:22:18 2015 +0200
+++ b/trytond/trytond/modules/stock/shipment.py	Mon Oct 05 12:23:46 2015 +0200
@@ -1177,14 +1177,17 @@
                     continue
                 key = cls._sync_inventory_to_outgoing_grouping_key(move,
                     'outgoing')
-                if outgoing_qty.get(key, 0.0) > 0.0:
+                if (outgoing_qty.get(key, 0.0)
+                        > move.product.default_uom.rounding):
                     exc_qty = Uom.compute_qty(move.product.default_uom,
                             outgoing_qty[key], move.uom)
                     removed_qty = Uom.compute_qty(move.uom,
                         min(exc_qty, move.quantity), move.product.default_uom,
                         round=False)
                     Move.write([move], {
-                            'quantity': max(0.0, move.quantity - exc_qty),
+                            'quantity': max(0.0, Uom.round(
+                                    move.quantity - exc_qty,
+                                    move.uom.rounding)),
                             })
                     outgoing_qty[key] -= removed_qty