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	$105.92	13.185%	$119.8856	$119.89	$119.90	$119.90
Purchase #2	$159.46	8.763%	$173.4335	$173.43	$173.45	$173.40
Purchase #3	$94.49	6.174%	$100.3238	$100.32	$100.30	$100.30
Purchase #4	$72.63	6.782%	$77.5558	$77.56	$77.55	$77.60
Purchase #5	$130.31	10.114%	$143.4896	$143.49	$143.50	$143.50
Purchase #6	$162.92	7.771%	$175.5805	$175.58	$175.60	$175.60
Purchase #7	$13.69	5.382%	$14.4268	$14.43	$14.45	$14.40
7 purchase totals =	$739.42		$804.6956	$804.70	$804.75	$804.70