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 $87.35   5.773%   $92.3927   $92.39   $92.40   $92.40  
  Purchase #2 $244.94   9.604%   $268.464   $268.46   $268.45   $268.50  
  Purchase #3 $73.99   3.726%   $76.7469   $76.75   $76.75   $76.70  
  Purchase #4 $213.39   3.568%   $221.0038   $221.00   $221.00   $221.00  
  Purchase #5 $33.44   9.259%   $36.5362   $36.54   $36.55   $36.50  
  Purchase #6 $41.35   13.555%   $46.955   $46.96   $46.95   $47.00  
  Purchase #7 $141.87   8.103%   $153.3657   $153.37   $153.35   $153.40  
  7 purchase totals = $836.33       $895.4643   $895.47   $895.45   $895.50