Absolutely. Your trade-in is actually worth the trade-in price plus sales tax so if you sell it yourself you need to get at least that much. In your example with a 7% sales tax the $27,000 trade is actually worth $28,890.
GA no longer charges sales tax - they replaced the 6%-7% sales tax (depending on the county) and the annual ad valorem tax ($100-$400 per vehicle per year) with a one time registration fee of 6.5%. One of the few times that government actually got something right and did something good for the people. Although you do lose the trade-in sales tax discount.