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 $216.73   13.323%   $245.6049   $245.60   $245.60   $245.60  
  Purchase #2 $167.83   5.256%   $176.6511   $176.65   $176.65   $176.70  
  Purchase #3 $152.50   10.672%   $168.7748   $168.77   $168.75   $168.80  
  Purchase #4 $71.29   9.564%   $78.1082   $78.11   $78.10   $78.10  
  Purchase #5 $76.73   10.725%   $84.9593   $84.96   $84.95   $85.00  
  Purchase #6 $190.96   4.452%   $199.4615   $199.46   $199.45   $199.50  
  Purchase #7 $68.63   11.120%   $76.2617   $76.26   $76.25   $76.30  
  7 purchase totals = $944.67       $1,029.8215   $1,029.81   $1,029.75   $1,030.00