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 $248.98   5.269%   $262.0988   $262.10   $262.10   $262.10  
  Purchase #2 $224.35   3.675%   $232.5949   $232.59   $232.60   $232.60  
  Purchase #3 $78.46   4.691%   $82.1406   $82.14   $82.15   $82.10  
  Purchase #4 $216.27   4.403%   $225.7924   $225.79   $225.80   $225.80  
  Purchase #5 $237.73   9.827%   $261.0917   $261.09   $261.10   $261.10  
  Purchase #6 $190.37   8.225%   $206.0279   $206.03   $206.05   $206.00  
  Purchase #7 $221.55   6.322%   $235.5564   $235.56   $235.55   $235.60  
  7 purchase totals = $1,417.71       $1,505.3027   $1,505.30   $1,505.35   $1,505.30