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	$241.77	10.358%	$266.8125	$266.81	$266.80	$266.80
Purchase #2	$182.83	12.520%	$205.7203	$205.72	$205.70	$205.70
Purchase #3	$66.71	6.183%	$70.8347	$70.83	$70.85	$70.80
Purchase #4	$51.57	4.153%	$53.7117	$53.71	$53.70	$53.70
Purchase #5	$205.96	9.866%	$226.28	$226.28	$226.30	$226.30
Purchase #6	$172.58	11.167%	$191.852	$191.85	$191.85	$191.90
Purchase #7	$141.32	10.309%	$155.8887	$155.89	$155.90	$155.90
7 purchase totals =	$1,062.74		$1,171.0999	$1,171.09	$1,171.10	$1,171.10