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 $84.76   11.192%   $94.2463   $94.25   $94.25   $94.20  
  Purchase #2 $30.92   13.756%   $35.1734   $35.17   $35.15   $35.20  
  Purchase #3 $155.66   6.676%   $166.0519   $166.05   $166.05   $166.10  
  Purchase #4 $31.91   7.115%   $34.1804   $34.18   $34.20   $34.20  
  Purchase #5 $161.54   13.570%   $183.461   $183.46   $183.45   $183.50  
  Purchase #6 $46.71   10.249%   $51.4973   $51.50   $51.50   $51.50  
  Purchase #7 $247.76   5.152%   $260.5246   $260.52   $260.50   $260.50  
  7 purchase totals = $759.26       $825.1349   $825.13   $825.10   $825.20