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 $68.91   8.745%   $74.9362   $74.94   $74.95   $74.90  
  Purchase #2 $237.86   3.535%   $246.2684   $246.27   $246.25   $246.30  
  Purchase #3 $111.66   6.713%   $119.1557   $119.16   $119.15   $119.20  
  Purchase #4 $115.32   4.403%   $120.3975   $120.40   $120.40   $120.40  
  Purchase #5 $107.73   6.866%   $115.1267   $115.13   $115.15   $115.10  
  Purchase #6 $161.93   11.546%   $180.6264   $180.63   $180.65   $180.60  
  Purchase #7 $151.63   4.322%   $158.1834   $158.18   $158.20   $158.20  
  7 purchase totals = $955.04       $1,014.6943   $1,014.71   $1,014.75   $1,014.70