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	$238.37	7.304%	$255.7805	$255.78	$255.80	$255.80
Purchase #2	$112.36	6.852%	$120.0589	$120.06	$120.05	$120.10
Purchase #3	$54.51	11.478%	$60.7667	$60.77	$60.75	$60.80
Purchase #4	$137.62	10.188%	$151.6407	$151.64	$151.65	$151.60
Purchase #5	$86.50	4.737%	$90.5975	$90.60	$90.60	$90.60
Purchase #6	$179.92	5.615%	$190.0225	$190.02	$190.00	$190.00
Purchase #7	$151.58	5.160%	$159.4015	$159.40	$159.40	$159.40
7 purchase totals =	$960.86		$1,028.2683	$1,028.27	$1,028.25	$1,028.30