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	$145.77	9.813%	$160.0744	$160.07	$160.05	$160.10
Purchase #2	$75.52	10.506%	$83.4541	$83.45	$83.45	$83.50
Purchase #3	$44.66	4.205%	$46.538	$46.54	$46.55	$46.50
Purchase #4	$113.80	11.357%	$126.7243	$126.72	$126.70	$126.70
Purchase #5	$52.67	13.579%	$59.8221	$59.82	$59.80	$59.80
Purchase #6	$87.91	4.179%	$91.5838	$91.58	$91.60	$91.60
Purchase #7	$214.49	11.624%	$239.4223	$239.42	$239.40	$239.40
7 purchase totals =	$734.82		$807.6190	$807.60	$807.55	$807.60