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	$205.76	9.345%	$224.9883	$224.99	$225.00	$225.00
Purchase #2	$105.39	5.588%	$111.2792	$111.28	$111.30	$111.30
Purchase #3	$74.26	6.194%	$78.8597	$78.86	$78.85	$78.90
Purchase #4	$40.63	6.434%	$43.2441	$43.24	$43.25	$43.20
Purchase #5	$30.48	13.474%	$34.5869	$34.59	$34.60	$34.60
Purchase #6	$16.84	3.130%	$17.3671	$17.37	$17.35	$17.40
Purchase #7	$55.77	13.262%	$63.1662	$63.17	$63.15	$63.20
7 purchase totals =	$529.13		$573.4915	$573.50	$573.50	$573.60