I see 27% federal tax deducted after I enter 1099-B form. Though I am in 22% tax bracket. What is the additional 5% for? State tax seems to be correct.

As you add income, some income-based credits such as the Earned income credit could decrease, which could give you the impression of a higher marginal tax rate.

The Earned Income Tax credit (EITC) is a bell shaped curve against income. The EITC rises with income until a certain level of income when it starts to decrease to reach 0 at the maximum level of income for the category.

As an example, please look at the EITC tables from page 33 of this IRS publication.

If you also collected Social Security, more of that may have become taxable as a result of the additional income. Or less of, say, your Medical expenses were deductible because of the 7.5% thresshold.