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	$238.34	7.444%	$256.082	$256.08	$256.10	$256.10
Purchase #2	$143.77	10.212%	$158.4518	$158.45	$158.45	$158.50
Purchase #3	$105.50	12.148%	$118.3161	$118.32	$118.30	$118.30
Purchase #4	$136.89	12.715%	$154.2956	$154.30	$154.30	$154.30
Purchase #5	$149.77	6.627%	$159.6953	$159.70	$159.70	$159.70
Purchase #6	$60.25	9.795%	$66.1515	$66.15	$66.15	$66.20
Purchase #7	$95.41	8.397%	$103.4216	$103.42	$103.40	$103.40
7 purchase totals =	$929.93		$1,016.4139	$1,016.42	$1,016.40	$1,016.50