My question is: why would you want to? PHP 7 was released in Dec 2015. PHP 5 won't be receiving any bug fixes any more, only security updates. Just replace php5-* with php7.0-* in your install command and you're good to go:
sudo apt-get install nginx php7.0-cli php7.0-fpm php7.0-gd php7.0-mcrypt php7.0-curl