What I'd do, since this is real life. I'd round the specs up to the nearest meter by 3 meters.

5 rolls is 1m x 3m.

\(\displaystyle

\text{Let the clients specs be $\ell_{spec} \times w_{spec}$}\\

L=3\left(\left \lfloor \dfrac{\ell}{3} \right\rfloor + 1\right)\\

W=\left \lfloor w\right\rfloor + 1\\

N_\ell = \left \lceil 5 \cdot \dfrac{L}{3} \cdot 1.1 \right \rceil\\

N_w = \lceil W \cdot 1.1 \rceil\\

\text{You would need to purchase $N_\ell \times N_w$ rolls of sod}

\)

Do you understand the symbols I used?

\(\displaystyle \lfloor x \rfloor = \text{the largest integer less than x}\\

\lceil x \rceil = \text{the least integer larger than x}\\

\text{for example, $\lfloor 10.4 \rfloor = 10$}\\

\text{$\lceil 10.4 \rceil = 11$} \)