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	$241.95	4.385%	$252.5595	$252.56	$252.55	$252.60
Purchase #2	$102.59	11.711%	$114.6043	$114.60	$114.60	$114.60
Purchase #3	$130.97	10.610%	$144.8659	$144.87	$144.85	$144.90
Purchase #4	$85.71	7.496%	$92.1348	$92.13	$92.15	$92.10
Purchase #5	$29.82	13.435%	$33.8263	$33.83	$33.85	$33.80
Purchase #6	$27.69	4.140%	$28.8364	$28.84	$28.85	$28.80
Purchase #7	$116.44	9.159%	$127.1047	$127.10	$127.10	$127.10
7 purchase totals =	$735.17		$793.9319	$793.93	$793.95	$793.90