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 $59.36   5.866%   $62.8421   $62.84   $62.85   $62.80  
  Purchase #2 $232.38   7.451%   $249.6946   $249.69   $249.70   $249.70  
  Purchase #3 $71.50   3.593%   $74.069   $74.07   $74.05   $74.10  
  Purchase #4 $172.47   13.610%   $195.9432   $195.94   $195.95   $195.90  
  Purchase #5 $54.69   13.614%   $62.1355   $62.14   $62.15   $62.10  
  Purchase #6 $171.83   10.240%   $189.4254   $189.43   $189.45   $189.40  
  Purchase #7 $117.38   3.283%   $121.2336   $121.23   $121.25   $121.20  
  7 purchase totals = $879.61       $955.3434   $955.34   $955.40   $955.20