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	$233.95	5.501%	$246.8196	$246.82	$246.80	$246.80
Purchase #2	$21.59	4.605%	$22.5842	$22.58	$22.60	$22.60
Purchase #3	$171.56	11.840%	$191.8727	$191.87	$191.85	$191.90
Purchase #4	$5.43	9.413%	$5.9411	$5.94	$5.95	$5.90
Purchase #5	$232.50	12.840%	$262.353	$262.35	$262.35	$262.40
Purchase #6	$24.87	10.602%	$27.5067	$27.51	$27.50	$27.50
Purchase #7	$103.81	7.776%	$111.8823	$111.88	$111.90	$111.90
7 purchase totals =	$793.71		$868.9596	$868.95	$868.95	$869.00