jmc

The actual cost of the fudge Anna purchases is $$\begin{array}{rl}\frac{7}{9}\cdot 10& =0.\overline{7}\cdot 10\\ & =7.\overline{7}\\ & =7.777\dots \end{array}$$To round to the nearest hundredth, we must look at the thousandths place, which here is 7. Since 7 is greater than or equal to 5, we round the hundredths place, which in $7.\overline{7}$ is 7, up to 8. So, rounding $7.\overline{7}$ to the nearest hundredth yields $\boxed{7.78}$ dollars.