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 $111.57   13.408%   $126.5293   $126.53   $126.55   $126.50  
  Purchase #2 $190.66   9.493%   $208.7594   $208.76   $208.75   $208.80  
  Purchase #3 $236.69   3.486%   $244.941   $244.94   $244.95   $244.90  
  Purchase #4 $180.41   3.754%   $187.1826   $187.18   $187.20   $187.20  
  Purchase #5 $65.47   4.282%   $68.2734   $68.27   $68.25   $68.30  
  Purchase #6 $75.80   12.120%   $84.987   $84.99   $85.00   $85.00  
  Purchase #7 $25.38   11.549%   $28.3111   $28.31   $28.30   $28.30  
  7 purchase totals = $885.98       $948.9838   $948.98   $949.00   $949.00