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	$204.62	8.806%	$222.6388	$222.64	$222.65	$222.60
Purchase #2	$152.82	10.267%	$168.51	$168.51	$168.50	$168.50
Purchase #3	$158.60	3.847%	$164.7013	$164.70	$164.70	$164.70
Purchase #4	$10.60	12.479%	$11.9228	$11.92	$11.90	$11.90
Purchase #5	$201.98	7.388%	$216.9023	$216.90	$216.90	$216.90
Purchase #6	$167.41	3.821%	$173.8067	$173.81	$173.80	$173.80
Purchase #7	$102.42	8.653%	$111.2824	$111.28	$111.30	$111.30
7 purchase totals =	$998.45		$1,069.7643	$1,069.76	$1,069.75	$1,069.70