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	$145.53	10.798%	$161.2443	$161.24	$161.25	$161.20
Purchase #2	$159.83	3.335%	$165.1603	$165.16	$165.15	$165.20
Purchase #3	$100.96	4.717%	$105.7223	$105.72	$105.70	$105.70
Purchase #4	$43.46	9.345%	$47.5213	$47.52	$47.50	$47.50
Purchase #5	$99.39	6.523%	$105.8732	$105.87	$105.85	$105.90
Purchase #6	$230.63	3.367%	$238.3953	$238.40	$238.40	$238.40
Purchase #7	$181.68	5.257%	$191.2309	$191.23	$191.25	$191.20
7 purchase totals =	$961.48		$1,015.1476	$1,015.14	$1,015.10	$1,015.10