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	$248.83	13.434%	$282.2578	$282.26	$282.25	$282.30
Purchase #2	$104.28	5.422%	$109.9341	$109.93	$109.95	$109.90
Purchase #3	$119.83	6.193%	$127.2511	$127.25	$127.25	$127.30
Purchase #4	$116.51	7.278%	$124.9896	$124.99	$125.00	$125.00
Purchase #5	$62.35	12.388%	$70.0739	$70.07	$70.05	$70.10
Purchase #6	$127.53	10.504%	$140.9258	$140.93	$140.95	$140.90
Purchase #7	$196.60	13.660%	$223.4556	$223.46	$223.45	$223.50
7 purchase totals =	$975.93		$1,078.8879	$1,078.89	$1,078.90	$1,079.00