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	$168.42	8.820%	$183.2746	$183.27	$183.25	$183.30
Purchase #2	$42.83	12.748%	$48.29	$48.29	$48.30	$48.30
Purchase #3	$118.31	7.371%	$127.0306	$127.03	$127.05	$127.00
Purchase #4	$133.91	9.738%	$146.9502	$146.95	$146.95	$147.00
Purchase #5	$108.28	3.509%	$112.0795	$112.08	$112.10	$112.10
Purchase #6	$118.44	11.566%	$132.1388	$132.14	$132.15	$132.10
Purchase #7	$238.32	6.126%	$252.9195	$252.92	$252.90	$252.90
7 purchase totals =	$928.51		$1,002.6832	$1,002.68	$1,002.70	$1,002.70