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	$197.59	12.439%	$222.1682	$222.17	$222.15	$222.20
Purchase #2	$154.51	8.547%	$167.716	$167.72	$167.70	$167.70
Purchase #3	$101.58	9.833%	$111.5684	$111.57	$111.55	$111.60
Purchase #4	$107.75	5.664%	$113.853	$113.85	$113.85	$113.90
Purchase #5	$57.64	8.768%	$62.6939	$62.69	$62.70	$62.70
Purchase #6	$20.65	9.795%	$22.6727	$22.67	$22.65	$22.70
Purchase #7	$192.43	3.113%	$198.4203	$198.42	$198.40	$198.40
7 purchase totals =	$832.15		$899.0925	$899.09	$899.00	$899.20