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	$93.83	7.821%	$101.1684	$101.17	$101.15	$101.20
Purchase #2	$102.47	8.602%	$111.2845	$111.28	$111.30	$111.30
Purchase #3	$46.98	3.775%	$48.7535	$48.75	$48.75	$48.80
Purchase #4	$162.26	12.484%	$182.5165	$182.52	$182.50	$182.50
Purchase #5	$99.27	12.309%	$111.4891	$111.49	$111.50	$111.50
Purchase #6	$238.83	6.548%	$254.4686	$254.47	$254.45	$254.50
Purchase #7	$167.83	3.169%	$173.1485	$173.15	$173.15	$173.10
7 purchase totals =	$911.47		$982.8291	$982.83	$982.80	$982.90