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	$188.59	4.168%	$196.4504	$196.45	$196.45	$196.50
Purchase #2	$241.95	13.864%	$275.4939	$275.49	$275.50	$275.50
Purchase #3	$105.75	9.694%	$116.0014	$116.00	$116.00	$116.00
Purchase #4	$158.68	9.486%	$173.7324	$173.73	$173.75	$173.70
Purchase #5	$75.86	12.273%	$85.1703	$85.17	$85.15	$85.20
Purchase #6	$86.37	7.411%	$92.7709	$92.77	$92.75	$92.80
Purchase #7	$130.87	13.129%	$148.0519	$148.05	$148.05	$148.10
7 purchase totals =	$988.07		$1,087.6712	$1,087.66	$1,087.65	$1,087.80