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	$41.60	4.642%	$43.5311	$43.53	$43.55	$43.50
Purchase #2	$153.78	12.466%	$172.9502	$172.95	$172.95	$173.00
Purchase #3	$122.29	4.487%	$127.7772	$127.78	$127.80	$127.80
Purchase #4	$40.65	7.832%	$43.8337	$43.83	$43.85	$43.80
Purchase #5	$57.84	4.625%	$60.5151	$60.52	$60.50	$60.50
Purchase #6	$239.52	9.692%	$262.7343	$262.73	$262.75	$262.70
Purchase #7	$134.89	13.549%	$153.1662	$153.17	$153.15	$153.20
7 purchase totals =	$790.57		$864.5078	$864.51	$864.55	$864.50