"Is there a minimum profit I need to reach before I report to the IRS"
No. Generally as a taxpayer you need to report all income from all sources.
This kind of question comes up all the time with respect to interest income since payers of interest aren't required to generate a 1099-MISC for amounts less than $10 but that doesn't mean you don't have to report your $2.51 interest income. You are obliged to do so.
As far as reporting this activity to the IRS, that's done on Schedule C which is incorporated into your income tax return. The profit will be taxed at "ordinary" tax rates, (like wages, interest, etc.), and is also subject to Self Employment taxes, (Medicare and Social Security), at roughly a 15% rate.
TurboTax supports the preparation of Schedule C and will calculate any SE Taxes for you, but you will need to use the TurboTax "Self-employed" version if you want to prepare your income taxes online. In the desktop versions all of them support the preparation of Schedule C though the version with the most "focus" on self-employment is the TurboTax "Home and Business" version.
