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 $104.48   9.368%   $114.2677   $114.27   $114.25   $114.30  
  Purchase #2 $98.61   7.134%   $105.6448   $105.64   $105.65   $105.60  
  Purchase #3 $130.54   7.416%   $140.2208   $140.22   $140.20   $140.20  
  Purchase #4 $121.53   6.429%   $129.3432   $129.34   $129.35   $129.30  
  Purchase #5 $164.70   8.386%   $178.5117   $178.51   $178.50   $178.50  
  Purchase #6 $24.96   10.721%   $27.636   $27.64   $27.65   $27.60  
  Purchase #7 $248.25   3.362%   $256.5962   $256.60   $256.60   $256.60  
  7 purchase totals = $893.07       $952.2204   $952.22   $952.20   $952.10