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 $104.80   13.791%   $119.253   $119.25   $119.25   $119.30  
  Purchase #2 $195.36   10.345%   $215.57   $215.57   $215.55   $215.60  
  Purchase #3 $245.66   9.378%   $268.698   $268.70   $268.70   $268.70  
  Purchase #4 $149.82   11.428%   $166.9414   $166.94   $166.95   $166.90  
  Purchase #5 $211.51   3.719%   $219.3761   $219.38   $219.40   $219.40  
  Purchase #6 $250.63   4.428%   $261.7279   $261.73   $261.75   $261.70  
  Purchase #7 $215.51   13.618%   $244.8582   $244.86   $244.85   $244.90  
  7 purchase totals = $1,373.29       $1,496.4246   $1,496.43   $1,496.45   $1,496.50