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	$33.90	11.666%	$37.8548	$37.85	$37.85	$37.90
Purchase #2	$141.86	13.745%	$161.3587	$161.36	$161.35	$161.40
Purchase #3	$238.31	6.195%	$253.0733	$253.07	$253.05	$253.10
Purchase #4	$203.64	13.758%	$231.6568	$231.66	$231.65	$231.70
Purchase #5	$127.77	11.277%	$142.1786	$142.18	$142.20	$142.20
Purchase #6	$62.89	11.773%	$70.294	$70.29	$70.30	$70.30
Purchase #7	$117.70	4.389%	$122.8659	$122.87	$122.85	$122.90
7 purchase totals =	$926.07		$1,019.2821	$1,019.28	$1,019.25	$1,019.50