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	$246.37	11.138%	$273.8107	$273.81	$273.80	$273.80
Purchase #2	$62.79	5.806%	$66.4356	$66.44	$66.45	$66.40
Purchase #3	$42.79	5.596%	$45.1845	$45.18	$45.20	$45.20
Purchase #4	$18.77	4.499%	$19.6145	$19.61	$19.60	$19.60
Purchase #5	$107.58	8.337%	$116.5489	$116.55	$116.55	$116.50
Purchase #6	$167.55	3.771%	$173.8683	$173.87	$173.85	$173.90
Purchase #7	$59.39	5.677%	$62.7616	$62.76	$62.75	$62.80
7 purchase totals =	$705.24		$758.2241	$758.22	$758.20	$758.20