Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $114.53   11.409%   $127.5967   $127.60   $127.60   $127.60  
  Purchase #2 $151.44   11.734%   $169.21   $169.21   $169.20   $169.20  
  Purchase #3 $88.27   8.103%   $95.4225   $95.42   $95.40   $95.40  
  Purchase #4 $78.50   4.644%   $82.1455   $82.15   $82.15   $82.10  
  Purchase #5 $102.26   10.836%   $113.3409   $113.34   $113.35   $113.30  
  Purchase #6 $227.98   10.611%   $252.171   $252.17   $252.15   $252.20  
  Purchase #7 $233.75   5.149%   $245.7858   $245.79   $245.80   $245.80  
  7 purchase totals = $996.73       $1,085.6724   $1,085.68   $1,085.65   $1,085.60