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	$204.41	11.560%	$228.0398	$228.04	$228.05	$228.00
Purchase #2	$18.36	10.666%	$20.3183	$20.32	$20.30	$20.30
Purchase #3	$18.90	13.843%	$21.5163	$21.52	$21.50	$21.50
Purchase #4	$14.63	6.720%	$15.6131	$15.61	$15.60	$15.60
Purchase #5	$60.29	5.757%	$63.7609	$63.76	$63.75	$63.80
Purchase #6	$74.29	9.239%	$81.1537	$81.15	$81.15	$81.20
Purchase #7	$101.55	9.423%	$111.1191	$111.12	$111.10	$111.10
7 purchase totals =	$492.43		$541.5212	$541.52	$541.45	$541.50