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	$108.90	7.323%	$116.8747	$116.87	$116.85	$116.90
Purchase #2	$165.66	11.847%	$185.2857	$185.29	$185.30	$185.30
Purchase #3	$88.96	12.702%	$100.2597	$100.26	$100.25	$100.30
Purchase #4	$87.74	3.286%	$90.6231	$90.62	$90.60	$90.60
Purchase #5	$30.66	9.330%	$33.5206	$33.52	$33.50	$33.50
Purchase #6	$121.68	4.832%	$127.5596	$127.56	$127.55	$127.60
Purchase #7	$187.81	10.433%	$207.4042	$207.40	$207.40	$207.40
7 purchase totals =	$791.41		$861.5276	$861.52	$861.45	$861.60