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	$66.30	8.683%	$72.0568	$72.06	$72.05	$72.10
Purchase #2	$74.32	4.653%	$77.7781	$77.78	$77.80	$77.80
Purchase #3	$63.79	13.840%	$72.6185	$72.62	$72.60	$72.60
Purchase #4	$12.54	13.600%	$14.2454	$14.25	$14.25	$14.20
Purchase #5	$95.75	3.485%	$99.0869	$99.09	$99.10	$99.10
Purchase #6	$183.45	4.604%	$191.896	$191.90	$191.90	$191.90
Purchase #7	$227.65	8.510%	$247.023	$247.02	$247.00	$247.00
7 purchase totals =	$723.80		$774.7047	$774.72	$774.70	$774.70