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 $24.85   4.756%   $26.0319   $26.03   $26.05   $26.00  
  Purchase #2 $176.59   4.663%   $184.8244   $184.82   $184.80   $184.80  
  Purchase #3 $236.80   7.809%   $255.2917   $255.29   $255.30   $255.30  
  Purchase #4 $121.40   3.478%   $125.6223   $125.62   $125.60   $125.60  
  Purchase #5 $97.42   6.354%   $103.6101   $103.61   $103.60   $103.60  
  Purchase #6 $73.76   3.602%   $76.4168   $76.42   $76.40   $76.40  
  Purchase #7 $104.98   9.762%   $115.2281   $115.23   $115.25   $115.20  
  7 purchase totals = $835.80       $887.0253   $887.02   $887.00   $886.90