I received a 1099 for $756. About how much in taxes do I owe on it.

Is it 1099-misc? If yes, you must file tax return. You will report your income and expenses on schedule C or C-EZ (Form 1040). This income is subject to SE tax at 15.3%. Read: Your U.S. Tax Return: Tax Filing by Self Employed Sole Proprietor or Independent Contractor

At most, $115 in self-employment taxes.

But that is if you have NO offsetting expenses.