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	$209.77	3.843%	$217.8315	$217.83	$217.85	$217.80
Purchase #2	$116.68	13.257%	$132.1483	$132.15	$132.15	$132.10
Purchase #3	$158.82	7.300%	$170.4139	$170.41	$170.40	$170.40
Purchase #4	$46.38	10.162%	$51.0931	$51.09	$51.10	$51.10
Purchase #5	$143.46	11.832%	$160.4342	$160.43	$160.45	$160.40
Purchase #6	$55.48	8.812%	$60.3689	$60.37	$60.35	$60.40
Purchase #7	$202.56	6.299%	$215.3193	$215.32	$215.30	$215.30
7 purchase totals =	$933.15		$1,007.6092	$1,007.60	$1,007.60	$1,007.50