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	$53.55	12.625%	$60.3107	$60.31	$60.30	$60.30
Purchase #2	$225.87	6.512%	$240.5787	$240.58	$240.60	$240.60
Purchase #3	$11.51	5.863%	$12.1848	$12.18	$12.20	$12.20
Purchase #4	$172.75	10.201%	$190.3722	$190.37	$190.35	$190.40
Purchase #5	$163.81	5.428%	$172.7016	$172.70	$172.70	$172.70
Purchase #6	$72.79	8.207%	$78.7639	$78.76	$78.75	$78.80
Purchase #7	$27.63	13.143%	$31.2614	$31.26	$31.25	$31.30
7 purchase totals =	$727.91		$786.1733	$786.16	$786.15	$786.30