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	$44.95	10.167%	$49.5201	$49.52	$49.50	$49.50
Purchase #2	$120.54	4.668%	$126.1668	$126.17	$126.15	$126.20
Purchase #3	$29.50	8.674%	$32.0588	$32.06	$32.05	$32.10
Purchase #4	$11.97	4.335%	$12.4889	$12.49	$12.50	$12.50
Purchase #5	$172.96	3.125%	$178.365	$178.37	$178.35	$178.40
Purchase #6	$100.37	12.191%	$112.6061	$112.61	$112.60	$112.60
Purchase #7	$214.63	3.559%	$222.2687	$222.27	$222.25	$222.30
7 purchase totals =	$694.92		$733.4744	$733.49	$733.40	$733.60