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	$174.47	6.433%	$185.6937	$185.69	$185.70	$185.70
Purchase #2	$9.91	6.855%	$10.5893	$10.59	$10.60	$10.60
Purchase #3	$93.83	11.148%	$104.2902	$104.29	$104.30	$104.30
Purchase #4	$214.52	7.643%	$230.9158	$230.92	$230.90	$230.90
Purchase #5	$111.83	13.831%	$127.2972	$127.30	$127.30	$127.30
Purchase #6	$48.56	3.637%	$50.3261	$50.33	$50.35	$50.30
Purchase #7	$25.77	5.770%	$27.2569	$27.26	$27.25	$27.30
7 purchase totals =	$678.89		$736.3692	$736.38	$736.40	$736.40