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 $86.58   8.594%   $94.0207   $94.02   $94.00   $94.00  
  Purchase #2 $161.75   13.259%   $183.1964   $183.20   $183.20   $183.20  
  Purchase #3 $50.64   7.808%   $54.594   $54.59   $54.60   $54.60  
  Purchase #4 $114.43   3.197%   $118.0883   $118.09   $118.10   $118.10  
  Purchase #5 $107.41   6.632%   $114.5334   $114.53   $114.55   $114.50  
  Purchase #6 $236.67   7.834%   $255.2107   $255.21   $255.20   $255.20  
  Purchase #7 $30.26   13.686%   $34.4014   $34.40   $34.40   $34.40  
  7 purchase totals = $787.74       $854.0449   $854.04   $854.05   $854.00