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	$144.95	6.204%	$153.9427	$153.94	$153.95	$153.90
Purchase #2	$228.91	6.733%	$244.3225	$244.32	$244.30	$244.30
Purchase #3	$152.77	13.190%	$172.9204	$172.92	$172.90	$172.90
Purchase #4	$175.72	5.615%	$185.5867	$185.59	$185.60	$185.60
Purchase #5	$107.48	5.617%	$113.5172	$113.52	$113.50	$113.50
Purchase #6	$18.63	12.261%	$20.9142	$20.91	$20.90	$20.90
Purchase #7	$61.78	5.235%	$65.0142	$65.01	$65.00	$65.00
7 purchase totals =	$890.24		$956.2179	$956.21	$956.15	$956.10