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 $48.26   10.423%   $53.2901   $53.29   $53.30   $53.30  
  Purchase #2 $25.76   3.854%   $26.7528   $26.75   $26.75   $26.80  
  Purchase #3 $111.38   12.788%   $125.6233   $125.62   $125.60   $125.60  
  Purchase #4 $195.54   11.431%   $217.8922   $217.89   $217.90   $217.90  
  Purchase #5 $245.37   6.269%   $260.7522   $260.75   $260.75   $260.80  
  Purchase #6 $142.48   7.137%   $152.6488   $152.65   $152.65   $152.60  
  Purchase #7 $244.80   5.578%   $258.4549   $258.45   $258.45   $258.50  
  7 purchase totals = $1,013.59       $1,095.4143   $1,095.40   $1,095.40   $1,095.50