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 $67.52   6.595%   $71.9729   $71.97   $71.95   $72.00  
  Purchase #2 $124.86   8.481%   $135.4494   $135.45   $135.45   $135.40  
  Purchase #3 $144.25   10.548%   $159.4655   $159.47   $159.45   $159.50  
  Purchase #4 $172.77   8.481%   $187.4226   $187.42   $187.40   $187.40  
  Purchase #5 $23.87   5.862%   $25.2693   $25.27   $25.25   $25.30  
  Purchase #6 $136.75   13.149%   $154.7313   $154.73   $154.75   $154.70  
  Purchase #7 $192.63   7.550%   $207.1736   $207.17   $207.15   $207.20  
  7 purchase totals = $862.65       $941.4846   $941.48   $941.40   $941.50