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	$103.87	7.249%	$111.3995	$111.40	$111.40	$111.40
Purchase #2	$36.50	5.123%	$38.3699	$38.37	$38.35	$38.40
Purchase #3	$17.35	12.472%	$19.5139	$19.51	$19.50	$19.50
Purchase #4	$41.42	5.317%	$43.6223	$43.62	$43.60	$43.60
Purchase #5	$221.66	4.384%	$231.3776	$231.38	$231.40	$231.40
Purchase #6	$88.26	8.151%	$95.4541	$95.45	$95.45	$95.50
Purchase #7	$68.45	9.236%	$74.772	$74.77	$74.75	$74.80
7 purchase totals =	$577.51		$614.5093	$614.50	$614.45	$614.60