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	$172.41	8.499%	$187.0631	$187.06	$187.05	$187.10
Purchase #2	$46.33	5.307%	$48.7887	$48.79	$48.80	$48.80
Purchase #3	$51.72	5.316%	$54.4694	$54.47	$54.45	$54.50
Purchase #4	$111.68	4.403%	$116.5973	$116.60	$116.60	$116.60
Purchase #5	$95.27	4.743%	$99.7887	$99.79	$99.80	$99.80
Purchase #6	$129.28	11.281%	$143.8641	$143.86	$143.85	$143.90
Purchase #7	$198.91	13.422%	$225.6077	$225.61	$225.60	$225.60
7 purchase totals =	$805.60		$876.1790	$876.18	$876.15	$876.30