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 $58.51   7.581%   $62.9456   $62.95   $62.95   $62.90  
  Purchase #2 $172.31   12.434%   $193.735   $193.74   $193.75   $193.70  
  Purchase #3 $67.95   8.475%   $73.7088   $73.71   $73.70   $73.70  
  Purchase #4 $195.38   13.797%   $222.3366   $222.34   $222.35   $222.30  
  Purchase #5 $45.78   8.663%   $49.7459   $49.75   $49.75   $49.70  
  Purchase #6 $130.57   7.580%   $140.4672   $140.47   $140.45   $140.50  
  Purchase #7 $46.42   4.779%   $48.6384   $48.64   $48.65   $48.60  
  7 purchase totals = $716.92       $791.5775   $791.60   $791.60   $791.40