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 $72.71   13.135%   $82.2605   $82.26   $82.25   $82.30  
  Purchase #2 $196.49   10.430%   $216.9839   $216.98   $217.00   $217.00  
  Purchase #3 $71.97   5.756%   $76.1126   $76.11   $76.10   $76.10  
  Purchase #4 $69.25   10.473%   $76.5026   $76.50   $76.50   $76.50  
  Purchase #5 $154.57   6.248%   $164.2275   $164.23   $164.25   $164.20  
  Purchase #6 $170.78   6.802%   $182.3965   $182.40   $182.40   $182.40  
  Purchase #7 $195.62   7.345%   $209.9883   $209.99   $210.00   $210.00  
  7 purchase totals = $931.39       $1,008.4719   $1,008.47   $1,008.50   $1,008.50