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 $69.62   9.707%   $76.378   $76.38   $76.40   $76.40  
  Purchase #2 $181.84   4.285%   $189.6318   $189.63   $189.65   $189.60  
  Purchase #3 $11.48   5.149%   $12.0711   $12.07   $12.05   $12.10  
  Purchase #4 $151.68   8.554%   $164.6547   $164.65   $164.65   $164.70  
  Purchase #5 $83.82   12.866%   $94.6043   $94.60   $94.60   $94.60  
  Purchase #6 $43.96   8.555%   $47.7208   $47.72   $47.70   $47.70  
  Purchase #7 $125.32   5.517%   $132.2339   $132.23   $132.25   $132.20  
  7 purchase totals = $667.72       $717.2946   $717.28   $717.30   $717.30