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	$111.87	4.830%	$117.2733	$117.27	$117.25	$117.30
Purchase #2	$145.67	9.615%	$159.6762	$159.68	$159.70	$159.70
Purchase #3	$228.62	12.318%	$256.7814	$256.78	$256.80	$256.80
Purchase #4	$25.30	8.777%	$27.5206	$27.52	$27.50	$27.50
Purchase #5	$235.31	10.565%	$260.1705	$260.17	$260.15	$260.20
Purchase #6	$37.50	5.530%	$39.5738	$39.57	$39.55	$39.60
Purchase #7	$233.25	4.873%	$244.6163	$244.62	$244.60	$244.60
7 purchase totals =	$1,017.52		$1,105.6121	$1,105.61	$1,105.55	$1,105.70