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	$200.81	5.870%	$212.5975	$212.60	$212.60	$212.60
Purchase #2	$183.44	4.153%	$191.0583	$191.06	$191.05	$191.10
Purchase #3	$46.71	12.847%	$52.7108	$52.71	$52.70	$52.70
Purchase #4	$65.85	9.536%	$72.1295	$72.13	$72.15	$72.10
Purchase #5	$46.85	3.344%	$48.4167	$48.42	$48.40	$48.40
Purchase #6	$69.73	11.692%	$77.8828	$77.88	$77.90	$77.90
Purchase #7	$49.32	11.823%	$55.1511	$55.15	$55.15	$55.20
7 purchase totals =	$662.71		$709.9467	$709.95	$709.95	$710.00