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	$116.93	5.422%	$123.2699	$123.27	$123.25	$123.30
Purchase #2	$241.91	8.536%	$262.5594	$262.56	$262.55	$262.60
Purchase #3	$119.92	5.370%	$126.3597	$126.36	$126.35	$126.40
Purchase #4	$30.84	5.512%	$32.5399	$32.54	$32.55	$32.50
Purchase #5	$184.37	4.267%	$192.2371	$192.24	$192.25	$192.20
Purchase #6	$48.59	10.381%	$53.6341	$53.63	$53.65	$53.60
Purchase #7	$216.45	5.152%	$227.6015	$227.60	$227.60	$227.60
7 purchase totals =	$959.01		$1,018.2016	$1,018.20	$1,018.20	$1,018.20