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 $233.41   5.647%   $246.5907   $246.59   $246.60   $246.60  
  Purchase #2 $234.30   4.776%   $245.4902   $245.49   $245.50   $245.50  
  Purchase #3 $189.60   13.538%   $215.268   $215.27   $215.25   $215.30  
  Purchase #4 $163.79   3.198%   $169.028   $169.03   $169.05   $169.00  
  Purchase #5 $241.42   8.453%   $261.8272   $261.83   $261.85   $261.80  
  Purchase #6 $192.43   3.812%   $199.7654   $199.77   $199.75   $199.80  
  Purchase #7 $208.73   10.688%   $231.0391   $231.04   $231.05   $231.00  
  7 purchase totals = $1,463.68       $1,569.0086   $1,569.02   $1,569.05   $1,569.00