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	$230.44	7.237%	$247.1169	$247.12	$247.10	$247.10
Purchase #2	$11.88	4.767%	$12.4463	$12.45	$12.45	$12.40
Purchase #3	$59.28	3.352%	$61.2671	$61.27	$61.25	$61.30
Purchase #4	$159.37	8.230%	$172.4862	$172.49	$172.50	$172.50
Purchase #5	$237.92	9.178%	$259.7563	$259.76	$259.75	$259.80
Purchase #6	$32.40	3.796%	$33.6299	$33.63	$33.65	$33.60
Purchase #7	$99.49	11.142%	$110.5752	$110.58	$110.60	$110.60
7 purchase totals =	$830.78		$897.2779	$897.30	$897.30	$897.30