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	$9.82	9.547%	$10.7575	$10.76	$10.75	$10.80
Purchase #2	$61.33	6.858%	$65.536	$65.54	$65.55	$65.50
Purchase #3	$133.77	13.512%	$151.845	$151.85	$151.85	$151.80
Purchase #4	$188.71	5.129%	$198.3889	$198.39	$198.40	$198.40
Purchase #5	$167.59	3.523%	$173.4942	$173.49	$173.50	$173.50
Purchase #6	$132.30	8.655%	$143.7506	$143.75	$143.75	$143.80
Purchase #7	$208.87	4.489%	$218.2462	$218.25	$218.25	$218.20
7 purchase totals =	$902.39		$962.0184	$962.03	$962.05	$962.00