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	$183.67	11.653%	$205.0731	$205.07	$205.05	$205.10
Purchase #2	$18.71	9.383%	$20.4656	$20.47	$20.45	$20.50
Purchase #3	$224.71	4.765%	$235.4174	$235.42	$235.40	$235.40
Purchase #4	$46.85	11.617%	$52.2926	$52.29	$52.30	$52.30
Purchase #5	$95.83	4.116%	$99.7744	$99.77	$99.75	$99.80
Purchase #6	$207.92	9.291%	$227.2378	$227.24	$227.25	$227.20
Purchase #7	$22.83	12.141%	$25.6018	$25.60	$25.60	$25.60
7 purchase totals =	$800.52		$865.8627	$865.86	$865.80	$865.90