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	$118.67	7.445%	$127.505	$127.51	$127.50	$127.50
Purchase #2	$204.42	6.362%	$217.4252	$217.43	$217.45	$217.40
Purchase #3	$136.59	5.395%	$143.959	$143.96	$143.95	$144.00
Purchase #4	$32.48	4.636%	$33.9858	$33.99	$34.00	$34.00
Purchase #5	$112.56	13.627%	$127.8986	$127.90	$127.90	$127.90
Purchase #6	$153.67	3.358%	$158.8302	$158.83	$158.85	$158.80
Purchase #7	$169.80	11.205%	$188.8261	$188.83	$188.85	$188.80
7 purchase totals =	$928.19		$998.4299	$998.45	$998.50	$998.40