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 $177.54   10.259%   $195.7538   $195.75   $195.75   $195.80  
  Purchase #2 $116.27   8.229%   $125.8379   $125.84   $125.85   $125.80  
  Purchase #3 $179.49   3.543%   $185.8493   $185.85   $185.85   $185.80  
  Purchase #4 $51.97   12.292%   $58.3582   $58.36   $58.35   $58.40  
  Purchase #5 $32.90   3.872%   $34.1739   $34.17   $34.15   $34.20  
  Purchase #6 $240.25   5.571%   $253.6343   $253.63   $253.65   $253.60  
  Purchase #7 $97.48   5.429%   $102.7722   $102.77   $102.75   $102.80  
  7 purchase totals = $895.90       $956.3796   $956.37   $956.35   $956.40