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	$21.58	9.153%	$23.5552	$23.56	$23.55	$23.60
Purchase #2	$81.80	8.593%	$88.8291	$88.83	$88.85	$88.80
Purchase #3	$65.71	3.833%	$68.2287	$68.23	$68.25	$68.20
Purchase #4	$13.91	5.199%	$14.6332	$14.63	$14.65	$14.60
Purchase #5	$46.51	6.276%	$49.429	$49.43	$49.45	$49.40
Purchase #6	$106.46	4.527%	$111.2794	$111.28	$111.30	$111.30
Purchase #7	$103.27	7.610%	$111.1288	$111.13	$111.15	$111.10
7 purchase totals =	$439.24		$467.0834	$467.09	$467.20	$467.00