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	$134.40	7.743%	$144.8066	$144.81	$144.80	$144.80
Purchase #2	$37.62	7.434%	$40.4167	$40.42	$40.40	$40.40
Purchase #3	$45.39	10.724%	$50.2576	$50.26	$50.25	$50.30
Purchase #4	$37.89	11.244%	$42.1504	$42.15	$42.15	$42.20
Purchase #5	$68.27	3.291%	$70.5168	$70.52	$70.50	$70.50
Purchase #6	$236.60	6.567%	$252.1375	$252.14	$252.15	$252.10
Purchase #7	$114.29	3.461%	$118.2456	$118.25	$118.25	$118.20
7 purchase totals =	$674.46		$718.5312	$718.55	$718.50	$718.50