Taxes associated with self-publishing in the United States are, to my knowledge:
1. Federal taxes - the income you receive from self-publishing. You will receive a 1099 from whatever sales channel(s) you are using for your books (Amazon, B&N, Smashwords, etc.). You will use this information to file your annual taxes.
2. State taxes - if your state has a state tax, you will use the income noted on the 1099 as in #1 above.
3. If you are selling your books directly (i.e., from your own website or face-to-face or through the mail), you will need to pay sales tax on these items and you need to be registered as a business so you can file yearly, quarterly and/or monthly sales tax (and business and operating taxes) reports (if you sell enough to be required to report monthly).
4. Social Security and Medicare taxes. If writing is your full-time income, or the primary source of your income, you will need to pay your own Social Security and Medicare taxes. I am researching the estimated quarterly payment process right now.
I am just learning about all of the particulars relating to writing as a full-time job. In a lot of ways, it's easier if you have a full-time job and write on the side. But, it's not more fun!