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 $67.32   12.315%   $75.6105   $75.61   $75.60   $75.60  
  Purchase #2 $12.90   13.552%   $14.6482   $14.65   $14.65   $14.60  
  Purchase #3 $235.46   6.466%   $250.6848   $250.68   $250.70   $250.70  
  Purchase #4 $221.34   3.224%   $228.476   $228.48   $228.50   $228.50  
  Purchase #5 $164.62   4.826%   $172.5646   $172.56   $172.55   $172.60  
  Purchase #6 $194.63   7.138%   $208.5227   $208.52   $208.50   $208.50  
  Purchase #7 $136.89   5.733%   $144.7379   $144.74   $144.75   $144.70  
  7 purchase totals = $1,033.16       $1,095.2447   $1,095.24   $1,095.25   $1,095.20