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	$78.69	9.863%	$86.4512	$86.45	$86.45	$86.50
Purchase #2	$230.76	3.495%	$238.8251	$238.83	$238.85	$238.80
Purchase #3	$71.51	4.849%	$74.9775	$74.98	$75.00	$75.00
Purchase #4	$132.31	13.856%	$150.6429	$150.64	$150.65	$150.60
Purchase #5	$149.91	11.212%	$166.7179	$166.72	$166.70	$166.70
Purchase #6	$109.78	4.389%	$114.5982	$114.60	$114.60	$114.60
Purchase #7	$32.32	6.786%	$34.5132	$34.51	$34.50	$34.50
7 purchase totals =	$805.28		$866.7260	$866.73	$866.75	$866.70