diff --git a/sale.py b/sale.py
index 03f31f8..0bf9ff4 100644
--- a/sale.py
+++ b/sale.py
@@ -47,6 +47,7 @@ class Sale(metaclass=PoolMeta):
         self.tax_amount = Decimal('0.0')
         self.total_amount = Decimal('0.0')
         self.total_discount = Decimal('0.0')
+        self.total_tip = Decimal('0.0')
 
         if self.lines:
             for line in self.lines:
@@ -57,6 +58,7 @@ class Sale(metaclass=PoolMeta):
             self.tax_amount = self.currency.round(self.tax_amount)
         self.total_amount = self.untaxed_amount + self.tax_amount
         if self.currency:
+            self.total_tip = self.currency.round(self.total_tip)
             self.total_discount = self.currency.round(self.total_discount)
             self.total_amount = self.currency.round(self.total_amount)