Index: payment/uc_payment/uc_payment.module
===================================================================
--- payment/uc_payment/uc_payment.module	(revision 754)
+++ payment/uc_payment/uc_payment.module	(working copy)
@@ -343,11 +343,12 @@ function uc_payment_get_totals() {
         $output .= '<tr><td align="right"><b>'. $line[2] .':</b></td>'
                   .'<td align="right">'. uc_price($line[1], $context) .'</td></tr>';
         if ($line[3]) {
-          $grand_total += round($line[1], 2);
+          $grand_total += $line[1];
         }
       }
     }
 
+    $grand_total = round($grand_total, 3);
     $context['subject'] = array(
       'grand_total' => $grand_total,
     );