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	$184.73	11.256%	$205.5232	$205.52	$205.50	$205.50
Purchase #2	$34.74	13.478%	$39.4223	$39.42	$39.40	$39.40
Purchase #3	$155.26	11.858%	$173.6707	$173.67	$173.65	$173.70
Purchase #4	$190.30	13.302%	$215.6137	$215.61	$215.60	$215.60
Purchase #5	$146.84	12.108%	$164.6194	$164.62	$164.60	$164.60
Purchase #6	$33.32	12.610%	$37.5217	$37.52	$37.50	$37.50
Purchase #7	$206.90	6.627%	$220.6113	$220.61	$220.60	$220.60
7 purchase totals =	$952.09		$1,056.9823	$1,056.97	$1,056.85	$1,056.90