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	$139.82	6.505%	$148.9153	$148.92	$148.90	$148.90
Purchase #2	$48.65	4.602%	$50.8889	$50.89	$50.90	$50.90
Purchase #3	$76.88	13.563%	$87.3072	$87.31	$87.30	$87.30
Purchase #4	$11.95	12.160%	$13.4031	$13.40	$13.40	$13.40
Purchase #5	$5.74	11.604%	$6.4061	$6.41	$6.40	$6.40
Purchase #6	$49.60	5.748%	$52.451	$52.45	$52.45	$52.50
Purchase #7	$152.46	13.254%	$172.667	$172.67	$172.65	$172.70
7 purchase totals =	$485.10		$532.0386	$532.05	$532.00	$532.10