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 $158.62   11.364%   $176.6456   $176.65   $176.65   $176.60  
  Purchase #2 $164.99   4.692%   $172.7313   $172.73   $172.75   $172.70  
  Purchase #3 $89.79   8.184%   $97.1384   $97.14   $97.15   $97.10  
  Purchase #4 $139.86   8.733%   $152.074   $152.07   $152.05   $152.10  
  Purchase #5 $34.54   4.763%   $36.1851   $36.19   $36.20   $36.20  
  Purchase #6 $245.55   4.461%   $256.504   $256.50   $256.50   $256.50  
  Purchase #7 $60.88   7.198%   $65.2621   $65.26   $65.25   $65.30  
  7 purchase totals = $894.23       $956.5405   $956.54   $956.55   $956.50