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	$143.50	12.531%	$161.482	$161.48	$161.50	$161.50
Purchase #2	$70.91	5.177%	$74.581	$74.58	$74.60	$74.60
Purchase #3	$128.92	13.365%	$146.1502	$146.15	$146.15	$146.20
Purchase #4	$107.30	4.209%	$111.8163	$111.82	$111.80	$111.80
Purchase #5	$10.61	11.837%	$11.8659	$11.87	$11.85	$11.90
Purchase #6	$48.59	12.665%	$54.7439	$54.74	$54.75	$54.70
Purchase #7	$136.30	5.186%	$143.3685	$143.37	$143.35	$143.40
7 purchase totals =	$646.13		$704.0078	$704.01	$704.00	$704.10