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 $107.95   5.766%   $114.1744   $114.17   $114.15   $114.20  
  Purchase #2 $83.34   11.107%   $92.5966   $92.60   $92.60   $92.60  
  Purchase #3 $99.64   5.474%   $105.0943   $105.09   $105.10   $105.10  
  Purchase #4 $209.26   13.510%   $237.531   $237.53   $237.55   $237.50  
  Purchase #5 $238.70   3.534%   $247.1357   $247.14   $247.15   $247.10  
  Purchase #6 $33.65   9.119%   $36.7185   $36.72   $36.70   $36.70  
  Purchase #7 $95.82   5.847%   $101.4226   $101.42   $101.40   $101.40  
  7 purchase totals = $868.36       $934.6731   $934.67   $934.65   $934.60