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	$111.50	6.636%	$118.8991	$118.90	$118.90	$118.90
Purchase #2	$111.65	5.647%	$117.9549	$117.95	$117.95	$118.00
Purchase #3	$126.38	10.698%	$139.9001	$139.90	$139.90	$139.90
Purchase #4	$156.29	5.177%	$164.3811	$164.38	$164.40	$164.40
Purchase #5	$100.25	11.233%	$111.5111	$111.51	$111.50	$111.50
Purchase #6	$242.63	4.810%	$254.3005	$254.30	$254.30	$254.30
Purchase #7	$184.92	4.197%	$192.6811	$192.68	$192.70	$192.70
7 purchase totals =	$1,033.62		$1,099.6279	$1,099.62	$1,099.65	$1,099.70