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 $216.50   8.311%   $234.4933   $234.49   $234.50   $234.50  
  Purchase #2 $224.43   6.282%   $238.5287   $238.53   $238.55   $238.50  
  Purchase #3 $132.66   8.807%   $144.3434   $144.34   $144.35   $144.30  
  Purchase #4 $224.83   10.309%   $248.0077   $248.01   $248.00   $248.00  
  Purchase #5 $177.85   11.773%   $198.7883   $198.79   $198.80   $198.80  
  Purchase #6 $249.91   4.819%   $261.9532   $261.95   $261.95   $262.00  
  Purchase #7 $159.46   12.163%   $178.8551   $178.86   $178.85   $178.90  
  7 purchase totals = $1,385.64       $1,504.9697   $1,504.97   $1,505.00   $1,505.00