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	$162.91	11.408%	$181.4948	$181.49	$181.50	$181.50
Purchase #2	$196.77	7.159%	$210.8568	$210.86	$210.85	$210.90
Purchase #3	$212.68	13.821%	$242.0745	$242.07	$242.05	$242.10
Purchase #4	$106.95	4.498%	$111.7606	$111.76	$111.75	$111.80
Purchase #5	$100.39	3.681%	$104.0854	$104.09	$104.10	$104.10
Purchase #6	$146.65	6.768%	$156.5753	$156.58	$156.60	$156.60
Purchase #7	$228.45	10.153%	$251.6445	$251.64	$251.65	$251.60
7 purchase totals =	$1,154.80		$1,258.4919	$1,258.49	$1,258.50	$1,258.60