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 $63.29   10.328%   $69.8266   $69.83   $69.85   $69.80  
  Purchase #2 $193.57   11.431%   $215.697   $215.70   $215.70   $215.70  
  Purchase #3 $99.92   4.257%   $104.1736   $104.17   $104.15   $104.20  
  Purchase #4 $191.73   9.525%   $209.9923   $209.99   $210.00   $210.00  
  Purchase #5 $57.38   8.428%   $62.216   $62.22   $62.20   $62.20  
  Purchase #6 $125.42   9.566%   $137.4177   $137.42   $137.40   $137.40  
  Purchase #7 $140.45   8.381%   $152.2211   $152.22   $152.20   $152.20  
  7 purchase totals = $871.76       $951.5443   $951.55   $951.50   $951.50