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 $41.41   7.177%   $44.382   $44.38   $44.40   $44.40  
  Purchase #2 $111.45   12.407%   $125.2776   $125.28   $125.30   $125.30  
  Purchase #3 $10.64   11.405%   $11.8535   $11.85   $11.85   $11.90  
  Purchase #4 $184.49   4.818%   $193.3787   $193.38   $193.40   $193.40  
  Purchase #5 $136.75   13.239%   $154.8543   $154.85   $154.85   $154.90  
  Purchase #6 $182.39   10.158%   $200.9172   $200.92   $200.90   $200.90  
  Purchase #7 $215.77   3.645%   $223.6348   $223.63   $223.65   $223.60  
  7 purchase totals = $882.90       $954.2981   $954.29   $954.35   $954.40