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	$202.85	9.198%	$221.5081	$221.51	$221.50	$221.50
Purchase #2	$148.48	6.191%	$157.6724	$157.67	$157.65	$157.70
Purchase #3	$51.99	4.795%	$54.4829	$54.48	$54.50	$54.50
Purchase #4	$121.87	13.121%	$137.8606	$137.86	$137.85	$137.90
Purchase #5	$104.97	5.752%	$111.0079	$111.01	$111.00	$111.00
Purchase #6	$122.27	4.357%	$127.5973	$127.60	$127.60	$127.60
Purchase #7	$132.29	6.631%	$141.0621	$141.06	$141.05	$141.10
7 purchase totals =	$884.72		$951.1913	$951.19	$951.15	$951.30