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 $184.82   5.749%   $195.4453   $195.45   $195.45   $195.40  
  Purchase #2 $213.70   12.807%   $241.0686   $241.07   $241.05   $241.10  
  Purchase #3 $38.87   4.867%   $40.7618   $40.76   $40.75   $40.80  
  Purchase #4 $97.69   5.138%   $102.7093   $102.71   $102.70   $102.70  
  Purchase #5 $173.59   10.776%   $192.2961   $192.30   $192.30   $192.30  
  Purchase #6 $11.69   5.302%   $12.3098   $12.31   $12.30   $12.30  
  Purchase #7 $109.47   4.447%   $114.3381   $114.34   $114.35   $114.30  
  7 purchase totals = $829.83       $898.9290   $898.94   $898.90   $898.90