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	$151.41	7.390%	$162.5992	$162.60	$162.60	$162.60
Purchase #2	$127.70	4.712%	$133.7172	$133.72	$133.70	$133.70
Purchase #3	$107.42	3.422%	$111.0959	$111.10	$111.10	$111.10
Purchase #4	$38.58	11.797%	$43.1313	$43.13	$43.15	$43.10
Purchase #5	$145.77	9.191%	$159.1677	$159.17	$159.15	$159.20
Purchase #6	$30.31	13.205%	$34.3124	$34.31	$34.30	$34.30
Purchase #7	$157.73	9.670%	$172.9825	$172.98	$173.00	$173.00
7 purchase totals =	$758.92		$817.0062	$817.01	$817.00	$817.00