5K to invest help

[heyyo2]

I have 5000 dollars taht i want to put in such as a savings account. Im 21 years old. I heard CDs are good but there is penalty for withdrawing early. Some people say just put it on savings accounts but savings account opened at banks have very low interest which is basically nothing. I have another bank that i have 1K in but the interest they pay is 0.25 percent.

I see things online like INGDirect where it pays 4.2 percent on your money. However, they have 2 rates. One that is APY and the other is the regular rate on bankrate.com? I am also not sure how it works.

If i put in 5K at ing direct and say I want to take all my 5K out after 6 months, do i make 5000 X 0.042 X 6/12= 105 dollars?

Of course after taxes I would probably make only 70 or so? Do i have to pay taxes on this? I do not have a job so basically that is my income. I heard you had to make a certain amount to be taxed.

So if i only make 105 dollars for the year, do i still have to pay tax on this?

Any other recommendatoins would be great. Thanks.