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 $67.97   12.163%   $76.2372   $76.24   $76.25   $76.20  
  Purchase #2 $125.34   3.756%   $130.0478   $130.05   $130.05   $130.00  
  Purchase #3 $76.39   11.784%   $85.3918   $85.39   $85.40   $85.40  
  Purchase #4 $115.44   8.567%   $125.3297   $125.33   $125.35   $125.30  
  Purchase #5 $220.82   5.344%   $232.6206   $232.62   $232.60   $232.60  
  Purchase #6 $95.66   6.267%   $101.655   $101.66   $101.65   $101.70  
  Purchase #7 $176.41   7.840%   $190.2405   $190.24   $190.25   $190.20  
  7 purchase totals = $878.03       $941.5226   $941.53   $941.55   $941.40