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	$194.59	5.418%	$205.1329	$205.13	$205.15	$205.10
Purchase #2	$120.97	5.714%	$127.8822	$127.88	$127.90	$127.90
Purchase #3	$34.79	8.290%	$37.6741	$37.67	$37.65	$37.70
Purchase #4	$183.54	11.178%	$204.0561	$204.06	$204.05	$204.10
Purchase #5	$242.26	11.176%	$269.335	$269.34	$269.35	$269.30
Purchase #6	$223.62	6.720%	$238.6473	$238.65	$238.65	$238.60
Purchase #7	$15.62	13.277%	$17.6939	$17.69	$17.70	$17.70
7 purchase totals =	$1,015.39		$1,100.4215	$1,100.42	$1,100.45	$1,100.40