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 $231.63   4.598%   $242.2803   $242.28   $242.30   $242.30  
  Purchase #2 $208.42   13.669%   $236.9089   $236.91   $236.90   $236.90  
  Purchase #3 $237.80   10.175%   $261.9962   $262.00   $262.00   $262.00  
  Purchase #4 $97.32   13.430%   $110.3901   $110.39   $110.40   $110.40  
  Purchase #5 $173.84   10.809%   $192.6304   $192.63   $192.65   $192.60  
  Purchase #6 $242.57   13.475%   $275.2563   $275.26   $275.25   $275.30  
  Purchase #7 $32.69   4.541%   $34.1745   $34.17   $34.15   $34.20  
  7 purchase totals = $1,224.27       $1,353.6367   $1,353.64   $1,353.65   $1,353.70