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 $244.81   7.131%   $262.2674   $262.27   $262.25   $262.30  
  Purchase #2 $66.45   10.523%   $73.4425   $73.44   $73.45   $73.40  
  Purchase #3 $236.73   3.181%   $244.2604   $244.26   $244.25   $244.30  
  Purchase #4 $224.69   5.154%   $236.2705   $236.27   $236.25   $236.30  
  Purchase #5 $179.91   10.798%   $199.3367   $199.34   $199.35   $199.30  
  Purchase #6 $244.84   6.462%   $260.6616   $260.66   $260.65   $260.70  
  Purchase #7 $175.35   10.705%   $194.1212   $194.12   $194.10   $194.10  
  7 purchase totals = $1,372.78       $1,470.3603   $1,470.36   $1,470.30   $1,470.40