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	$100.84	10.778%	$111.7085	$111.71	$111.70	$111.70
Purchase #2	$249.79	6.657%	$266.4185	$266.42	$266.40	$266.40
Purchase #3	$51.87	3.439%	$53.6538	$53.65	$53.65	$53.70
Purchase #4	$12.67	7.637%	$13.6376	$13.64	$13.65	$13.60
Purchase #5	$18.51	5.468%	$19.5221	$19.52	$19.50	$19.50
Purchase #6	$72.85	7.818%	$78.5454	$78.55	$78.55	$78.50
Purchase #7	$81.66	6.257%	$86.7695	$86.77	$86.75	$86.80
7 purchase totals =	$588.19		$630.2554	$630.26	$630.20	$630.20