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	$102.37	8.551%	$111.1237	$111.12	$111.10	$111.10
Purchase #2	$97.29	3.163%	$100.3673	$100.37	$100.35	$100.40
Purchase #3	$205.45	5.635%	$217.0271	$217.03	$217.05	$217.00
Purchase #4	$175.25	9.422%	$191.7621	$191.76	$191.75	$191.80
Purchase #5	$102.88	11.210%	$114.4128	$114.41	$114.40	$114.40
Purchase #6	$129.41	10.199%	$142.6085	$142.61	$142.60	$142.60
Purchase #7	$68.76	7.350%	$73.8139	$73.81	$73.80	$73.80
7 purchase totals =	$881.41		$951.1154	$951.11	$951.05	$951.10