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	$230.67	12.798%	$260.1911	$260.19	$260.20	$260.20
Purchase #2	$27.47	11.637%	$30.6667	$30.67	$30.65	$30.70
Purchase #3	$32.54	4.697%	$34.0684	$34.07	$34.05	$34.10
Purchase #4	$122.28	4.253%	$127.4806	$127.48	$127.50	$127.50
Purchase #5	$14.28	11.156%	$15.8731	$15.87	$15.85	$15.90
Purchase #6	$111.40	11.153%	$123.8244	$123.82	$123.80	$123.80
Purchase #7	$93.68	6.671%	$99.9294	$99.93	$99.95	$99.90
7 purchase totals =	$632.32		$692.0337	$692.03	$692.00	$692.10