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	$138.64	11.265%	$154.2578	$154.26	$154.25	$154.30
Purchase #2	$122.46	5.237%	$128.8732	$128.87	$128.85	$128.90
Purchase #3	$248.49	7.159%	$266.2794	$266.28	$266.30	$266.30
Purchase #4	$68.75	6.105%	$72.9472	$72.95	$72.95	$72.90
Purchase #5	$224.52	4.143%	$233.8219	$233.82	$233.80	$233.80
Purchase #6	$129.35	11.301%	$143.9678	$143.97	$143.95	$144.00
Purchase #7	$101.65	9.645%	$111.4541	$111.45	$111.45	$111.50
7 purchase totals =	$1,033.86		$1,111.6014	$1,111.60	$1,111.55	$1,111.70