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	$235.52	8.525%	$255.5981	$255.60	$255.60	$255.60
Purchase #2	$12.48	8.162%	$13.4986	$13.50	$13.50	$13.50
Purchase #3	$163.64	7.739%	$176.3041	$176.30	$176.30	$176.30
Purchase #4	$118.96	7.163%	$127.4811	$127.48	$127.50	$127.50
Purchase #5	$94.35	13.141%	$106.7485	$106.75	$106.75	$106.70
Purchase #6	$115.42	10.712%	$127.7838	$127.78	$127.80	$127.80
Purchase #7	$83.85	5.868%	$88.7703	$88.77	$88.75	$88.80
7 purchase totals =	$824.22		$896.1845	$896.18	$896.20	$896.20