diff -r 9b5fafd2c656 trytond/trytond/modules/account_invoice/invoice.py
--- a/trytond/trytond/modules/account_invoice/invoice.py	Tue Mar 08 10:16:56 2016 +0100
+++ b/trytond/trytond/modules/account_invoice/invoice.py	Tue Mar 08 10:18:43 2016 +0100
@@ -464,8 +464,7 @@
         def round_taxes():
             if self.currency:
                 for value in computed_taxes.itervalues():
-                    for field in ('base', 'amount'):
-                        value[field] = self.currency.round(value[field])
+                    value['amount'] = self.currency.round(value['amount'])

         if self.lines:
             context = self.get_tax_context()
@@ -482,6 +481,8 @@
                 for tax in taxes:
                     key, val = self._compute_tax(tax,
                         self.type or 'out_invoice')
+                    if self.currency:
+                        val['base'] = self.currency.round(val['base'])
                     if key not in computed_taxes:
                         computed_taxes[key] = val
                     else:
@@ -845,8 +846,7 @@

         def round_taxes():
             for value in taxes.itervalues():
-                for field in ('base', 'amount'):
-                    value[field] = self.currency.round(value[field])
+                value['amount'] = self.currency.round(value['amount'])

         for line in self.lines:
             if line.type != 'line':
@@ -858,6 +858,8 @@
             for tax in tax_list:
                 key, val = self._compute_tax(tax, self.type)
                 val['invoice'] = self.id
+                if self.currency:
+                    val['base'] = self.currency.round(val['base'])
                 if key not in taxes:
                     taxes[key] = val
                 else: