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	$165.88	11.162%	$184.3955	$184.40	$184.40	$184.40
Purchase #2	$32.63	6.577%	$34.7761	$34.78	$34.80	$34.80
Purchase #3	$182.52	11.775%	$204.0117	$204.01	$204.00	$204.00
Purchase #4	$58.58	7.338%	$62.8786	$62.88	$62.90	$62.90
Purchase #5	$80.82	11.176%	$89.8524	$89.85	$89.85	$89.90
Purchase #6	$48.97	8.421%	$53.0938	$53.09	$53.10	$53.10
Purchase #7	$139.62	4.777%	$146.2896	$146.29	$146.30	$146.30
7 purchase totals =	$709.02		$775.2977	$775.30	$775.35	$775.40