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 $82.30   5.644%   $86.945   $86.95   $86.95   $86.90  
  Purchase #2 $57.92   8.595%   $62.8982   $62.90   $62.90   $62.90  
  Purchase #3 $96.28   5.700%   $101.768   $101.77   $101.75   $101.80  
  Purchase #4 $104.29   11.219%   $115.9903   $115.99   $116.00   $116.00  
  Purchase #5 $233.65   11.464%   $260.4356   $260.44   $260.45   $260.40  
  Purchase #6 $154.54   3.732%   $160.3074   $160.31   $160.30   $160.30  
  Purchase #7 $44.63   5.303%   $46.9967   $47.00   $47.00   $47.00  
  7 purchase totals = $773.61       $835.3412   $835.36   $835.35   $835.30