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	$49.63	4.209%	$51.7189	$51.72	$51.70	$51.70
Purchase #2	$195.46	12.249%	$219.4019	$219.40	$219.40	$219.40
Purchase #3	$248.89	3.577%	$257.7928	$257.79	$257.80	$257.80
Purchase #4	$170.81	11.626%	$190.6684	$190.67	$190.65	$190.70
Purchase #5	$105.51	5.472%	$111.2835	$111.28	$111.30	$111.30
Purchase #6	$12.86	13.346%	$14.5763	$14.58	$14.60	$14.60
Purchase #7	$158.79	9.275%	$173.5178	$173.52	$173.50	$173.50
7 purchase totals =	$941.95		$1,018.9596	$1,018.96	$1,018.95	$1,019.00