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	$105.50	11.607%	$117.7454	$117.75	$117.75	$117.70
Purchase #2	$74.60	4.296%	$77.8048	$77.80	$77.80	$77.80
Purchase #3	$148.41	11.699%	$165.7725	$165.77	$165.75	$165.80
Purchase #4	$14.43	8.249%	$15.6203	$15.62	$15.60	$15.60
Purchase #5	$21.72	12.679%	$24.4739	$24.47	$24.45	$24.50
Purchase #6	$139.54	4.475%	$145.7844	$145.78	$145.80	$145.80
Purchase #7	$188.51	6.291%	$200.3692	$200.37	$200.35	$200.40
7 purchase totals =	$692.71		$747.5705	$747.56	$747.50	$747.60