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	$61.75	11.104%	$68.6067	$68.61	$68.60	$68.60
Purchase #2	$173.42	10.397%	$191.4505	$191.45	$191.45	$191.50
Purchase #3	$48.59	10.506%	$53.6949	$53.69	$53.70	$53.70
Purchase #4	$68.78	5.625%	$72.6489	$72.65	$72.65	$72.60
Purchase #5	$65.30	13.472%	$74.0972	$74.10	$74.10	$74.10
Purchase #6	$240.99	10.307%	$265.8288	$265.83	$265.85	$265.80
Purchase #7	$231.51	10.296%	$255.3463	$255.35	$255.35	$255.30
7 purchase totals =	$890.34		$981.6733	$981.68	$981.70	$981.60