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	$116.75	13.500%	$132.5113	$132.51	$132.50	$132.50
Purchase #2	$120.67	5.522%	$127.3334	$127.33	$127.35	$127.30
Purchase #3	$100.74	7.220%	$108.0134	$108.01	$108.00	$108.00
Purchase #4	$77.37	12.556%	$87.0846	$87.08	$87.10	$87.10
Purchase #5	$98.54	4.672%	$103.1438	$103.14	$103.15	$103.10
Purchase #6	$67.41	7.249%	$72.2966	$72.30	$72.30	$72.30
Purchase #7	$63.45	4.786%	$66.4867	$66.49	$66.50	$66.50
7 purchase totals =	$644.93		$696.8698	$696.86	$696.90	$696.80