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	$51.86	5.330%	$54.6241	$54.62	$54.60	$54.60
Purchase #2	$204.94	4.476%	$214.1131	$214.11	$214.10	$214.10
Purchase #3	$65.62	8.304%	$71.0691	$71.07	$71.05	$71.10
Purchase #4	$65.27	10.421%	$72.0718	$72.07	$72.05	$72.10
Purchase #5	$20.42	4.549%	$21.3489	$21.35	$21.35	$21.30
Purchase #6	$74.52	6.763%	$79.5598	$79.56	$79.55	$79.60
Purchase #7	$241.97	8.471%	$262.4673	$262.47	$262.45	$262.50
7 purchase totals =	$724.60		$775.2541	$775.25	$775.15	$775.30