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	$100.98	8.389%	$109.4512	$109.45	$109.45	$109.50
Purchase #2	$118.83	10.750%	$131.6042	$131.60	$131.60	$131.60
Purchase #3	$140.52	3.149%	$144.945	$144.95	$144.95	$144.90
Purchase #4	$135.71	12.382%	$152.5136	$152.51	$152.50	$152.50
Purchase #5	$73.28	3.339%	$75.7268	$75.73	$75.75	$75.70
Purchase #6	$157.47	4.435%	$164.4538	$164.45	$164.45	$164.50
Purchase #7	$192.31	11.433%	$214.2968	$214.30	$214.30	$214.30
7 purchase totals =	$919.10		$992.9914	$992.99	$993.00	$993.00