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	$140.54	12.422%	$157.9979	$158.00	$158.00	$158.00
Purchase #2	$10.26	11.439%	$11.4336	$11.43	$11.45	$11.40
Purchase #3	$136.60	12.687%	$153.9304	$153.93	$153.95	$153.90
Purchase #4	$164.70	9.543%	$180.4173	$180.42	$180.40	$180.40
Purchase #5	$140.98	7.192%	$151.1193	$151.12	$151.10	$151.10
Purchase #6	$118.84	10.764%	$131.6319	$131.63	$131.65	$131.60
Purchase #7	$99.61	12.204%	$111.7664	$111.77	$111.75	$111.80
7 purchase totals =	$811.53		$898.2968	$898.30	$898.30	$898.20