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 $62.88   6.730%   $67.1118   $67.11   $67.10   $67.10  
  Purchase #2 $224.95   10.672%   $248.9567   $248.96   $248.95   $249.00  
  Purchase #3 $32.65   5.638%   $34.4908   $34.49   $34.50   $34.50  
  Purchase #4 $37.86   8.432%   $41.0524   $41.05   $41.05   $41.10  
  Purchase #5 $129.98   7.490%   $139.7155   $139.72   $139.70   $139.70  
  Purchase #6 $19.26   9.509%   $21.0914   $21.09   $21.10   $21.10  
  Purchase #7 $231.35   4.682%   $242.1818   $242.18   $242.20   $242.20  
  7 purchase totals = $738.93       $794.6004   $794.60   $794.60   $794.70