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	$51.29	13.576%	$58.2531	$58.25	$58.25	$58.30
Purchase #2	$90.40	4.541%	$94.5051	$94.51	$94.50	$94.50
Purchase #3	$118.26	7.749%	$127.424	$127.42	$127.40	$127.40
Purchase #4	$139.42	10.295%	$153.7733	$153.77	$153.75	$153.80
Purchase #5	$159.89	7.808%	$172.3742	$172.37	$172.35	$172.40
Purchase #6	$61.32	9.733%	$67.2883	$67.29	$67.30	$67.30
Purchase #7	$221.68	7.405%	$238.0954	$238.10	$238.10	$238.10
7 purchase totals =	$842.26		$911.7134	$911.71	$911.65	$911.80