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	$121.83	4.686%	$127.539	$127.54	$127.55	$127.50
Purchase #2	$237.72	7.456%	$255.4444	$255.44	$255.45	$255.40
Purchase #3	$66.77	11.538%	$74.4739	$74.47	$74.45	$74.50
Purchase #4	$247.59	12.816%	$279.3211	$279.32	$279.30	$279.30
Purchase #5	$134.85	11.622%	$150.5223	$150.52	$150.50	$150.50
Purchase #6	$125.38	10.239%	$138.2177	$138.22	$138.20	$138.20
Purchase #7	$237.92	10.378%	$262.6113	$262.61	$262.60	$262.60
7 purchase totals =	$1,172.06		$1,288.1297	$1,288.12	$1,288.05	$1,288.00