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 $92.41   10.192%   $101.8284   $101.83   $101.85   $101.80  
  Purchase #2 $126.32   13.350%   $143.1837   $143.18   $143.20   $143.20  
  Purchase #3 $42.65   8.238%   $46.1635   $46.16   $46.15   $46.20  
  Purchase #4 $245.62   6.382%   $261.2955   $261.30   $261.30   $261.30  
  Purchase #5 $195.54   11.322%   $217.679   $217.68   $217.70   $217.70  
  Purchase #6 $78.26   4.763%   $81.9875   $81.99   $82.00   $82.00  
  Purchase #7 $19.49   5.653%   $20.5918   $20.59   $20.60   $20.60  
  7 purchase totals = $800.29       $872.7294   $872.73   $872.80   $872.80