【Answer】Profit, 600
【Analysis】Percentage application problem
Purchase price: 21 yuan per share, at that time it increased by $5 \%$, we can find the original stock price $21 \div(1+5 \%)=20$ yuan per share;
Closing price: $20 \times(1-6 \%)=19.2$ yuan per share;
Second day's selling price: $19.2 \times(1+10 \%)=21.12$ yuan per share;
Since $21.12>21$, therefore, the total profit is $(21.12-21) \times 5000=600$ yuan.
5. Stock investor Xiao Li bought 5000 shares at 21 yuan per share when a certain stock increased by $5 \%$. On that day, the stock market closed with the stock falling by $6 \%$. The next day, when the stock rose by $10 \%$, Xiao Li sold the 5000 shares. Without considering transaction fees and other costs, Xiao Li made a profit or loss of $\qquad$ yuan from buying and selling this stock. （Note: Fill in the first blank with "profit" or "loss"）