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 $43.94   12.259%   $49.3266   $49.33   $49.35   $49.30  
  Purchase #2 $87.26   8.869%   $94.9991   $95.00   $95.00   $95.00  
  Purchase #3 $71.46   7.625%   $76.9088   $76.91   $76.90   $76.90  
  Purchase #4 $86.34   12.785%   $97.3786   $97.38   $97.40   $97.40  
  Purchase #5 $162.81   5.873%   $172.3718   $172.37   $172.35   $172.40  
  Purchase #6 $239.78   11.737%   $267.923   $267.92   $267.90   $267.90  
  Purchase #7 $116.29   6.237%   $123.543   $123.54   $123.55   $123.50  
  7 purchase totals = $807.88       $882.4509   $882.45   $882.45   $882.40