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 $117.29   6.816%   $125.2845   $125.28   $125.30   $125.30  
  Purchase #2 $184.48   6.459%   $196.3956   $196.40   $196.40   $196.40  
  Purchase #3 $55.72   5.533%   $58.803   $58.80   $58.80   $58.80  
  Purchase #4 $66.70   4.815%   $69.9116   $69.91   $69.90   $69.90  
  Purchase #5 $91.34   6.676%   $97.4379   $97.44   $97.45   $97.40  
  Purchase #6 $131.79   4.495%   $137.714   $137.71   $137.70   $137.70  
  Purchase #7 $205.41   10.554%   $227.089   $227.09   $227.10   $227.10  
  7 purchase totals = $852.73       $912.6356   $912.63   $912.65   $912.60