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	$54.32	9.360%	$59.4044	$59.40	$59.40	$59.40
Purchase #2	$214.81	12.301%	$241.2338	$241.23	$241.25	$241.20
Purchase #3	$52.90	11.672%	$59.0745	$59.07	$59.05	$59.10
Purchase #4	$153.83	12.352%	$172.8311	$172.83	$172.85	$172.80
Purchase #5	$40.26	10.583%	$44.5207	$44.52	$44.50	$44.50
Purchase #6	$173.94	10.498%	$192.2002	$192.20	$192.20	$192.20
Purchase #7	$42.32	5.548%	$44.6679	$44.67	$44.65	$44.70
7 purchase totals =	$732.38		$813.9326	$813.92	$813.90	$813.90