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	$143.43	7.149%	$153.6838	$153.68	$153.70	$153.70
Purchase #2	$199.52	4.531%	$208.5603	$208.56	$208.55	$208.60
Purchase #3	$163.60	5.185%	$172.0827	$172.08	$172.10	$172.10
Purchase #4	$46.81	6.769%	$49.9786	$49.98	$50.00	$50.00
Purchase #5	$176.72	5.168%	$185.8529	$185.85	$185.85	$185.90
Purchase #6	$104.86	11.250%	$116.6568	$116.66	$116.65	$116.70
Purchase #7	$133.40	13.287%	$151.1249	$151.12	$151.10	$151.10
7 purchase totals =	$968.34		$1,037.9400	$1,037.93	$1,037.95	$1,038.10