diff --git a/product/ERP5/Document/InvoiceTransactionRule.py b/product/ERP5/Document/InvoiceTransactionRule.py
index b73e3876507fce1ddc4e982e10b61a4f3376136b..68821fc86b5b2c72e60425cc1cd583d0ee93b6a8 100644
--- a/product/ERP5/Document/InvoiceTransactionRule.py
+++ b/product/ERP5/Document/InvoiceTransactionRule.py
@@ -263,6 +263,7 @@ class InvoiceTransactionRule(Rule, PredicateMatrix):
               # XXX this happen in many order, so this log is probably useless
               LOG("InvoiceTransactionRule", PROBLEM,
                   "expanding %s: without resource" % applied_rule.getPath())
+          quantity_precision = self.getQuantityPrecisionFromResource(resource)
           my_simulation_movement._edit(
                 source = transaction_line.getSource()
               , destination = transaction_line.getDestination()
@@ -271,9 +272,9 @@ class InvoiceTransactionRule(Rule, PredicateMatrix):
                                         .getDestinationSection()
               , resource = resource
                 # calculate (quantity * price) * cell_quantity
-              , quantity = (my_invoice_line_simulation.getQuantity()
+              , quantity = round((my_invoice_line_simulation.getQuantity()
                             * my_invoice_line_simulation.getPrice())
-                            * transaction_line.getQuantity()
+                            * transaction_line.getQuantity(), quantity_precision)
               , start_date = my_invoice_line_simulation.getStartDate()
               , stop_date  = my_invoice_line_simulation.getStopDate()
               , force_update = 1
diff --git a/product/ERP5Type/Base.py b/product/ERP5Type/Base.py
index 70818e5ab48d49fb4f8e076b3c70d95d39b85337..220fedfac394ee1b65d518dd6d8875645a22ad6e 100644
--- a/product/ERP5Type/Base.py
+++ b/product/ERP5Type/Base.py
@@ -2335,12 +2335,33 @@ class Base( CopyContainer, PortalContent, ActiveObject, Historical, ERP5Property
     # Add to catalog
     self.reindexObject()
 
+  # ZODB Transaction Management
   security.declarePublic('serialize')
   def serialize(self):
     """Make the transaction accessing to this object atomic
     """
     self.id = self.id
 
+  # Helpers
+  def getQuantityPrecisionFromResource(self, resource):
+    """
+      Provides a quick access to precision without accessing the resource
+      value in ZODB
+    """
+    def cashed_getQuantityPrecisionFromResource(resource):
+      resource_value = self.portal_categories.resolveCategory(resource)
+      if resource_value is not None:
+        return resource_value.getQuantityPrecision()
+      else:
+        return 0
+
+    cashed_getQuantityPrecisionFromResource = CachingMethod(cashed_getQuantityPrecisionFromResource,
+                                                        id='Base_getQuantityPrecisionFromResource')
+
+    return cashed_getResourceQuantityPrecision(resource)
+
+
+  # Documentation Helpers
   security.declareProtected( Permissions.ManagePortal, 'asDocumentationHelper' )
   def asDocumentationHelper(self, item_id=None):
     """