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	$187.42	13.435%	$212.5999	$212.60	$212.60	$212.60
Purchase #2	$17.75	10.111%	$19.5447	$19.54	$19.55	$19.50
Purchase #3	$134.64	3.758%	$139.6998	$139.70	$139.70	$139.70
Purchase #4	$114.55	11.615%	$127.855	$127.86	$127.85	$127.90
Purchase #5	$14.94	10.312%	$16.4806	$16.48	$16.50	$16.50
Purchase #6	$98.62	13.337%	$111.7729	$111.77	$111.75	$111.80
Purchase #7	$226.98	12.103%	$254.4514	$254.45	$254.45	$254.50
7 purchase totals =	$794.90		$882.4043	$882.40	$882.40	$882.50