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 $67.71   6.823%   $72.3299   $72.33   $72.35   $72.30  
  Purchase #2 $192.63   11.775%   $215.3122   $215.31   $215.30   $215.30  
  Purchase #3 $61.68   5.602%   $65.1353   $65.14   $65.15   $65.10  
  Purchase #4 $60.98   13.491%   $69.2068   $69.21   $69.20   $69.20  
  Purchase #5 $116.83   7.678%   $125.8002   $125.80   $125.80   $125.80  
  Purchase #6 $21.75   5.765%   $23.0039   $23.00   $23.00   $23.00  
  Purchase #7 $177.37   7.276%   $190.2754   $190.28   $190.30   $190.30  
  7 purchase totals = $698.95       $761.0637   $761.07   $761.10   $761.00