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 $32.92   3.268%   $33.9958   $34.00   $34.00   $34.00  
  Purchase #2 $196.34   6.226%   $208.5641   $208.56   $208.55   $208.60  
  Purchase #3 $234.32   4.871%   $245.7337   $245.73   $245.75   $245.70  
  Purchase #4 $146.90   4.311%   $153.2329   $153.23   $153.25   $153.20  
  Purchase #5 $213.56   6.299%   $227.0121   $227.01   $227.00   $227.00  
  Purchase #6 $69.78   5.738%   $73.784   $73.78   $73.80   $73.80  
  Purchase #7 $229.61   13.664%   $260.9839   $260.98   $261.00   $261.00  
  7 purchase totals = $1,123.43       $1,203.3065   $1,203.29   $1,203.35   $1,203.30