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	$11.69	3.820%	$12.1366	$12.14	$12.15	$12.10
Purchase #2	$177.47	8.617%	$192.7626	$192.76	$192.75	$192.80
Purchase #3	$43.81	10.848%	$48.5625	$48.56	$48.55	$48.60
Purchase #4	$69.29	13.411%	$78.5825	$78.58	$78.60	$78.60
Purchase #5	$9.78	5.278%	$10.2962	$10.30	$10.30	$10.30
Purchase #6	$159.41	13.781%	$181.3783	$181.38	$181.40	$181.40
Purchase #7	$161.37	6.816%	$172.369	$172.37	$172.35	$172.40
7 purchase totals =	$632.82		$696.0877	$696.09	$696.10	$696.20