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	$111.85	3.323%	$115.5668	$115.57	$115.55	$115.60
Purchase #2	$112.59	9.772%	$123.5923	$123.59	$123.60	$123.60
Purchase #3	$145.96	8.669%	$158.6133	$158.61	$158.60	$158.60
Purchase #4	$49.54	8.747%	$53.8733	$53.87	$53.85	$53.90
Purchase #5	$164.76	5.563%	$173.9256	$173.93	$173.95	$173.90
Purchase #6	$18.43	8.821%	$20.0557	$20.06	$20.05	$20.10
Purchase #7	$64.56	9.575%	$70.7416	$70.74	$70.75	$70.70
7 purchase totals =	$667.69		$716.3686	$716.37	$716.35	$716.40