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 $201.48   11.188%   $224.0216   $224.02   $224.00   $224.00  
  Purchase #2 $224.81   5.246%   $236.6035   $236.60   $236.60   $236.60  
  Purchase #3 $117.92   8.455%   $127.8901   $127.89   $127.90   $127.90  
  Purchase #4 $25.79   7.153%   $27.6348   $27.63   $27.65   $27.60  
  Purchase #5 $176.92   3.281%   $182.7247   $182.72   $182.70   $182.70  
  Purchase #6 $189.53   3.733%   $196.6052   $196.61   $196.60   $196.60  
  Purchase #7 $182.88   9.401%   $200.0725   $200.07   $200.05   $200.10  
  7 purchase totals = $1,119.33       $1,195.5524   $1,195.54   $1,195.50   $1,195.50