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 $114.73   3.374%   $118.601   $118.60   $118.60   $118.60  
  Purchase #2 $7.37   11.417%   $8.2114   $8.21   $8.20   $8.20  
  Purchase #3 $43.51   11.672%   $48.5885   $48.59   $48.60   $48.60  
  Purchase #4 $66.38   7.247%   $71.1906   $71.19   $71.20   $71.20  
  Purchase #5 $224.93   10.699%   $248.9953   $249.00   $249.00   $249.00  
  Purchase #6 $214.61   12.575%   $241.5972   $241.60   $241.60   $241.60  
  Purchase #7 $176.99   10.610%   $195.7686   $195.77   $195.75   $195.80  
  7 purchase totals = $848.52       $932.9526   $932.96   $932.95   $933.00