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	$90.69	13.717%	$103.1299	$103.13	$103.15	$103.10
Purchase #2	$16.74	5.182%	$17.6075	$17.61	$17.60	$17.60
Purchase #3	$89.63	3.112%	$92.4193	$92.42	$92.40	$92.40
Purchase #4	$175.37	5.614%	$185.2153	$185.22	$185.20	$185.20
Purchase #5	$64.95	12.224%	$72.8895	$72.89	$72.90	$72.90
Purchase #6	$209.75	5.580%	$221.4541	$221.45	$221.45	$221.50
Purchase #7	$25.69	11.733%	$28.7042	$28.70	$28.70	$28.70
7 purchase totals =	$672.82		$721.4198	$721.42	$721.40	$721.40