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 $64.33   11.719%   $71.8688   $71.87   $71.85   $71.90  
  Purchase #2 $65.89   11.137%   $73.2282   $73.23   $73.25   $73.20  
  Purchase #3 $146.82   8.611%   $159.4627   $159.46   $159.45   $159.50  
  Purchase #4 $248.89   4.404%   $259.8511   $259.85   $259.85   $259.90  
  Purchase #5 $76.89   7.120%   $82.3646   $82.36   $82.35   $82.40  
  Purchase #6 $49.37   9.230%   $53.9269   $53.93   $53.95   $53.90  
  Purchase #7 $239.53   9.684%   $262.7261   $262.73   $262.75   $262.70  
  7 purchase totals = $891.72       $963.4284   $963.43   $963.45   $963.50