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 $88.88   6.862%   $94.9789   $94.98   $95.00   $95.00  
  Purchase #2 $122.51   8.369%   $132.7629   $132.76   $132.75   $132.80  
  Purchase #3 $89.47   13.314%   $101.382   $101.38   $101.40   $101.40  
  Purchase #4 $108.63   3.299%   $112.2137   $112.21   $112.20   $112.20  
  Purchase #5 $121.61   10.177%   $133.9862   $133.99   $134.00   $134.00  
  Purchase #6 $239.94   9.563%   $262.8855   $262.89   $262.90   $262.90  
  Purchase #7 $85.93   3.448%   $88.8929   $88.89   $88.90   $88.90  
  7 purchase totals = $856.97       $927.1021   $927.10   $927.15   $927.20