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 $59.26   6.733%   $63.25   $63.25   $63.25   $63.30  
  Purchase #2 $112.58   6.322%   $119.6973   $119.70   $119.70   $119.70  
  Purchase #3 $231.39   8.166%   $250.2853   $250.29   $250.30   $250.30  
  Purchase #4 $231.78   13.697%   $263.5269   $263.53   $263.55   $263.50  
  Purchase #5 $17.33   7.401%   $18.6126   $18.61   $18.60   $18.60  
  Purchase #6 $71.25   9.109%   $77.7402   $77.74   $77.75   $77.70  
  Purchase #7 $146.33   8.355%   $158.5559   $158.56   $158.55   $158.60  
  7 purchase totals = $869.92       $951.6682   $951.68   $951.70   $951.70