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	$214.37	6.399%	$228.0875	$228.09	$228.10	$228.10
Purchase #2	$40.65	11.559%	$45.3487	$45.35	$45.35	$45.30
Purchase #3	$166.82	11.327%	$185.7157	$185.72	$185.70	$185.70
Purchase #4	$11.38	11.348%	$12.6714	$12.67	$12.65	$12.70
Purchase #5	$250.63	12.748%	$282.5803	$282.58	$282.60	$282.60
Purchase #6	$86.66	6.246%	$92.0728	$92.07	$92.05	$92.10
Purchase #7	$157.25	9.775%	$172.6212	$172.62	$172.60	$172.60
7 purchase totals =	$927.76		$1,019.0976	$1,019.10	$1,019.05	$1,019.10