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	$239.75	13.498%	$272.1115	$272.11	$272.10	$272.10
Purchase #2	$216.49	11.551%	$241.4968	$241.50	$241.50	$241.50
Purchase #3	$116.30	9.286%	$127.0996	$127.10	$127.10	$127.10
Purchase #4	$164.55	4.667%	$172.2295	$172.23	$172.25	$172.20
Purchase #5	$58.61	10.677%	$64.8678	$64.87	$64.85	$64.90
Purchase #6	$105.31	12.776%	$118.7644	$118.76	$118.75	$118.80
Purchase #7	$162.74	9.719%	$178.5567	$178.56	$178.55	$178.60
7 purchase totals =	$1,063.75		$1,175.1263	$1,175.13	$1,175.10	$1,175.20