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	$144.83	4.140%	$150.826	$150.83	$150.85	$150.80
Purchase #2	$66.46	11.719%	$74.2484	$74.25	$74.25	$74.20
Purchase #3	$11.34	13.706%	$12.8943	$12.89	$12.90	$12.90
Purchase #4	$216.73	8.682%	$235.5465	$235.55	$235.55	$235.50
Purchase #5	$118.91	10.116%	$130.9389	$130.94	$130.95	$130.90
Purchase #6	$133.93	12.605%	$150.8119	$150.81	$150.80	$150.80
Purchase #7	$45.89	3.440%	$47.4686	$47.47	$47.45	$47.50
7 purchase totals =	$738.09		$802.7346	$802.74	$802.75	$802.60