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 $202.31   5.752%   $213.9469   $213.95   $213.95   $213.90  
  Purchase #2 $250.88   9.372%   $274.3925   $274.39   $274.40   $274.40  
  Purchase #3 $107.79   10.355%   $118.9517   $118.95   $118.95   $119.00  
  Purchase #4 $45.27   5.697%   $47.849   $47.85   $47.85   $47.80  
  Purchase #5 $69.71   13.549%   $79.155   $79.16   $79.15   $79.20  
  Purchase #6 $105.54   8.223%   $114.2186   $114.22   $114.20   $114.20  
  Purchase #7 $215.67   5.666%   $227.8899   $227.89   $227.90   $227.90  
  7 purchase totals = $997.17       $1,076.4036   $1,076.41   $1,076.40   $1,076.40