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	$226.51	11.326%	$252.1645	$252.16	$252.15	$252.20
Purchase #2	$35.86	4.123%	$37.3385	$37.34	$37.35	$37.30
Purchase #3	$21.98	10.308%	$24.2457	$24.25	$24.25	$24.20
Purchase #4	$96.82	4.174%	$100.8613	$100.86	$100.85	$100.90
Purchase #5	$244.48	3.779%	$253.7189	$253.72	$253.70	$253.70
Purchase #6	$191.56	7.222%	$205.3945	$205.39	$205.40	$205.40
Purchase #7	$95.37	13.243%	$107.9998	$108.00	$108.00	$108.00
7 purchase totals =	$912.58		$981.7232	$981.72	$981.70	$981.70