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 $119.30   4.752%   $124.9691   $124.97   $124.95   $125.00  
  Purchase #2 $246.28   6.142%   $261.4065   $261.41   $261.40   $261.40  
  Purchase #3 $5.38   7.512%   $5.7841   $5.78   $5.80   $5.80  
  Purchase #4 $169.81   3.797%   $176.2577   $176.26   $176.25   $176.30  
  Purchase #5 $18.94   11.577%   $21.1327   $21.13   $21.15   $21.10  
  Purchase #6 $82.38   13.184%   $93.241   $93.24   $93.25   $93.20  
  Purchase #7 $179.31   12.650%   $201.9927   $201.99   $202.00   $202.00  
  7 purchase totals = $821.40       $884.7838   $884.78   $884.80   $884.80