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 $94.30   3.870%   $97.9494   $97.95   $97.95   $97.90  
  Purchase #2 $116.61   9.421%   $127.5958   $127.60   $127.60   $127.60  
  Purchase #3 $67.32   5.533%   $71.0448   $71.04   $71.05   $71.00  
  Purchase #4 $109.41   4.583%   $114.4243   $114.42   $114.40   $114.40  
  Purchase #5 $104.44   10.336%   $115.2349   $115.23   $115.25   $115.20  
  Purchase #6 $245.92   6.490%   $261.8802   $261.88   $261.90   $261.90  
  Purchase #7 $5.75   7.534%   $6.1832   $6.18   $6.20   $6.20  
  7 purchase totals = $743.75       $794.3126   $794.30   $794.35   $794.20