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	$244.58	4.432%	$255.4198	$255.42	$255.40	$255.40
Purchase #2	$229.78	7.493%	$246.9974	$247.00	$247.00	$247.00
Purchase #3	$199.53	11.509%	$222.4939	$222.49	$222.50	$222.50
Purchase #4	$227.50	7.592%	$244.7718	$244.77	$244.75	$244.80
Purchase #5	$48.94	11.338%	$54.4888	$54.49	$54.50	$54.50
Purchase #6	$155.44	11.710%	$173.642	$173.64	$173.65	$173.60
Purchase #7	$206.25	13.140%	$233.3513	$233.35	$233.35	$233.40
7 purchase totals =	$1,312.02		$1,431.1650	$1,431.16	$1,431.15	$1,431.20