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	$186.37	7.798%	$200.9031	$200.90	$200.90	$200.90
Purchase #2	$14.44	7.304%	$15.4947	$15.49	$15.50	$15.50
Purchase #3	$127.49	13.599%	$144.8274	$144.83	$144.85	$144.80
Purchase #4	$56.43	8.205%	$61.0601	$61.06	$61.05	$61.10
Purchase #5	$11.58	10.622%	$12.81	$12.81	$12.80	$12.80
Purchase #6	$228.65	4.344%	$238.5826	$238.58	$238.60	$238.60
Purchase #7	$6.40	8.151%	$6.9217	$6.92	$6.90	$6.90
7 purchase totals =	$631.36		$680.5996	$680.59	$680.60	$680.60