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 $205.52   4.201%   $214.1539   $214.15   $214.15   $214.20  
  Purchase #2 $198.91   5.352%   $209.5557   $209.56   $209.55   $209.60  
  Purchase #3 $180.99   9.383%   $197.9723   $197.97   $197.95   $198.00  
  Purchase #4 $44.66   6.314%   $47.4798   $47.48   $47.50   $47.50  
  Purchase #5 $118.77   10.247%   $130.9404   $130.94   $130.95   $130.90  
  Purchase #6 $107.25   6.789%   $114.5312   $114.53   $114.55   $114.50  
  Purchase #7 $36.38   3.479%   $37.6457   $37.65   $37.65   $37.60  
  7 purchase totals = $892.48       $952.2790   $952.28   $952.30   $952.30