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	$206.66	9.113%	$225.4929	$225.49	$225.50	$225.50
Purchase #2	$126.61	4.664%	$132.5151	$132.52	$132.50	$132.50
Purchase #3	$197.67	3.788%	$205.1577	$205.16	$205.15	$205.20
Purchase #4	$104.88	6.160%	$111.3406	$111.34	$111.35	$111.30
Purchase #5	$72.40	12.412%	$81.3863	$81.39	$81.40	$81.40
Purchase #6	$117.57	8.658%	$127.7492	$127.75	$127.75	$127.70
Purchase #7	$193.29	10.816%	$214.1962	$214.20	$214.20	$214.20
7 purchase totals =	$1,019.08		$1,097.8380	$1,097.85	$1,097.85	$1,097.80