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	$107.68	9.373%	$117.7728	$117.77	$117.75	$117.80
Purchase #2	$137.98	7.694%	$148.5962	$148.60	$148.60	$148.60
Purchase #3	$186.79	10.103%	$205.6614	$205.66	$205.65	$205.70
Purchase #4	$77.51	7.380%	$83.2302	$83.23	$83.25	$83.20
Purchase #5	$156.38	11.149%	$173.8148	$173.81	$173.80	$173.80
Purchase #6	$231.86	4.725%	$242.8154	$242.82	$242.80	$242.80
Purchase #7	$114.53	11.425%	$127.6151	$127.62	$127.60	$127.60
7 purchase totals =	$1,012.73		$1,099.5059	$1,099.51	$1,099.45	$1,099.50