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	$46.38	4.692%	$48.5561	$48.56	$48.55	$48.60
Purchase #2	$66.70	8.680%	$72.4896	$72.49	$72.50	$72.50
Purchase #3	$82.64	10.642%	$91.4345	$91.43	$91.45	$91.40
Purchase #4	$154.25	11.360%	$171.7728	$171.77	$171.75	$171.80
Purchase #5	$87.91	6.274%	$93.4255	$93.43	$93.45	$93.40
Purchase #6	$210.61	9.245%	$230.0809	$230.08	$230.10	$230.10
Purchase #7	$226.69	12.509%	$255.0467	$255.05	$255.05	$255.00
7 purchase totals =	$875.18		$962.8061	$962.81	$962.85	$962.80