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	$127.77	12.393%	$143.6045	$143.60	$143.60	$143.60
Purchase #2	$69.97	13.527%	$79.4348	$79.43	$79.45	$79.40
Purchase #3	$102.67	3.210%	$105.9657	$105.97	$105.95	$106.00
Purchase #4	$152.75	3.713%	$158.4216	$158.42	$158.40	$158.40
Purchase #5	$127.47	13.422%	$144.579	$144.58	$144.60	$144.60
Purchase #6	$45.67	12.144%	$51.2162	$51.22	$51.20	$51.20
Purchase #7	$41.47	11.580%	$46.2722	$46.27	$46.25	$46.30
7 purchase totals =	$667.77		$729.4940	$729.49	$729.45	$729.50