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	$34.38	10.593%	$38.0219	$38.02	$38.00	$38.00
Purchase #2	$222.77	6.383%	$236.9894	$236.99	$237.00	$237.00
Purchase #3	$125.40	4.776%	$131.3891	$131.39	$131.40	$131.40
Purchase #4	$232.52	10.174%	$256.1766	$256.18	$256.20	$256.20
Purchase #5	$51.76	5.137%	$54.4189	$54.42	$54.40	$54.40
Purchase #6	$176.66	13.516%	$200.5374	$200.54	$200.55	$200.50
Purchase #7	$59.35	11.262%	$66.034	$66.03	$66.05	$66.00
7 purchase totals =	$902.84		$983.5673	$983.57	$983.60	$983.50