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	$105.81	11.393%	$117.8649	$117.86	$117.85	$117.90
Purchase #2	$146.38	9.487%	$160.2671	$160.27	$160.25	$160.30
Purchase #3	$117.85	3.852%	$122.3896	$122.39	$122.40	$122.40
Purchase #4	$171.89	5.679%	$181.6516	$181.65	$181.65	$181.70
Purchase #5	$112.49	13.246%	$127.3904	$127.39	$127.40	$127.40
Purchase #6	$90.25	12.603%	$101.6242	$101.62	$101.60	$101.60
Purchase #7	$208.72	10.288%	$230.1931	$230.19	$230.20	$230.20
7 purchase totals =	$953.39		$1,041.3809	$1,041.37	$1,041.35	$1,041.50