setting the right permissions for public web folder

I have configured my VPS server (ubuntu 18.04) to run multiple domains and one of the webserver will be an opencart store (actually I have to move an opencart store from a shared hosting to a vps server)

I am not sure what permissions to give the store to work properly. In the old hosting in Cpanel the permissions was 755 for folders and 644 for files.

I moved the store from Cpanel to the VPS (using ssh) to:

/var/www/opecart/public

All the content is in the public folder.

The persmissions that I give it:

sudo chown -R $USER:www-data /var/www/opencart/public
sudo chmod -R 755 /var/www/opencart/public

and it`s not loadind the page.....it complains:

Warning: fopen(/var/www/opencart/public/system/logs/error.log): failed to open stream: Permission denied in /var/www/opencart/public/system/library/log.php

If I set to 775 it work fine.

sudo chmod -R 775 /var/www/opencart/public

It is ok to leave this permissions 775 for opencart ????