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	$111.36	4.440%	$116.3044	$116.30	$116.30	$116.30
Purchase #2	$63.43	3.587%	$65.7052	$65.71	$65.70	$65.70
Purchase #3	$35.50	6.766%	$37.9019	$37.90	$37.90	$37.90
Purchase #4	$136.90	6.188%	$145.3714	$145.37	$145.35	$145.40
Purchase #5	$208.60	3.455%	$215.8071	$215.81	$215.80	$215.80
Purchase #6	$169.75	11.864%	$189.8891	$189.89	$189.90	$189.90
Purchase #7	$227.44	8.510%	$246.7951	$246.80	$246.80	$246.80
7 purchase totals =	$952.98		$1,017.7742	$1,017.78	$1,017.75	$1,017.80