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	$153.45	12.477%	$172.596	$172.60	$172.60	$172.60
Purchase #2	$56.68	8.466%	$61.4785	$61.48	$61.50	$61.50
Purchase #3	$92.48	12.535%	$104.0724	$104.07	$104.05	$104.10
Purchase #4	$138.62	8.460%	$150.3473	$150.35	$150.35	$150.30
Purchase #5	$102.29	8.621%	$111.1084	$111.11	$111.10	$111.10
Purchase #6	$12.44	9.195%	$13.5839	$13.58	$13.60	$13.60
Purchase #7	$243.49	12.172%	$273.1276	$273.13	$273.15	$273.10
7 purchase totals =	$799.45		$886.3141	$886.32	$886.35	$886.30