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	$149.45	3.447%	$154.6015	$154.60	$154.60	$154.60
Purchase #2	$13.72	11.433%	$15.2886	$15.29	$15.30	$15.30
Purchase #3	$45.47	5.712%	$48.0672	$48.07	$48.05	$48.10
Purchase #4	$214.28	7.257%	$229.8303	$229.83	$229.85	$229.80
Purchase #5	$55.68	11.186%	$61.9084	$61.91	$61.90	$61.90
Purchase #6	$148.80	13.131%	$168.3389	$168.34	$168.35	$168.30
Purchase #7	$94.58	11.103%	$105.0812	$105.08	$105.10	$105.10
7 purchase totals =	$721.98		$783.1161	$783.12	$783.15	$783.10