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 $107.49   6.178%   $114.1307   $114.13   $114.15   $114.10  
  Purchase #2 $249.89   4.706%   $261.6498   $261.65   $261.65   $261.60  
  Purchase #3 $234.26   10.832%   $259.635   $259.64   $259.65   $259.60  
  Purchase #4 $186.71   6.621%   $199.0721   $199.07   $199.05   $199.10  
  Purchase #5 $222.47   3.497%   $230.2498   $230.25   $230.25   $230.20  
  Purchase #6 $5.62   9.400%   $6.1483   $6.15   $6.15   $6.10  
  Purchase #7 $54.53   10.754%   $60.3942   $60.39   $60.40   $60.40  
  7 purchase totals = $1,060.97       $1,131.2799   $1,131.28   $1,131.30   $1,131.10