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 $117.81   7.124%   $126.2028   $126.20   $126.20   $126.20  
  Purchase #2 $168.28   8.157%   $182.0066   $182.01   $182.00   $182.00  
  Purchase #3 $107.92   6.342%   $114.7643   $114.76   $114.75   $114.80  
  Purchase #4 $206.45   13.758%   $234.8534   $234.85   $234.85   $234.90  
  Purchase #5 $226.42   5.737%   $239.4097   $239.41   $239.40   $239.40  
  Purchase #6 $69.69   7.765%   $75.1014   $75.10   $75.10   $75.10  
  Purchase #7 $32.62   6.108%   $34.6124   $34.61   $34.60   $34.60  
  7 purchase totals = $929.19       $1,006.9506   $1,006.94   $1,006.90   $1,007.00