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	$214.45	11.134%	$238.3269	$238.33	$238.35	$238.30
Purchase #2	$65.86	13.795%	$74.9454	$74.95	$74.95	$74.90
Purchase #3	$49.95	8.485%	$54.1883	$54.19	$54.20	$54.20
Purchase #4	$43.81	11.145%	$48.6926	$48.69	$48.70	$48.70
Purchase #5	$226.59	13.154%	$256.3956	$256.40	$256.40	$256.40
Purchase #6	$118.88	7.654%	$127.9791	$127.98	$128.00	$128.00
Purchase #7	$85.41	5.394%	$90.017	$90.02	$90.00	$90.00
7 purchase totals =	$804.95		$890.5449	$890.56	$890.60	$890.50