For the API it would be:
api.meraki.com
<shard>.meraki.com
Where <shard> is the shard your org is located on.
If you use MV, then there are going to be a bunch more for image retrieval (snapshot API).
If you use MQTT you are going to need to add in the MQTT servers that you use.
For the dashboard, that's a lot tougher. There are the obvious ones:
meraki.com
www.meraki.com
meraki.cisco.com
account.meraki.com
<shard>.meraki.com
That's assuming you use Meraki accounts. If you log in using SecureX or SAML you'll need to add all those authentication URLs as well.
But then you also need all the URLs for all the components used. If you go to Chrome developer tools (CTRL-SHIFT-I) and go to the "Sources" tab, and then load each page, you'll get the external domains also required. For example:
Note that you won't be able to match on IP address, as a lot of these use load balancers with dynamic sets of IPs growing and expanding, so you have to match on FQDN.
If you use MV you are going to need to add in the URLs for the cloud proxies (if viewing from outside) or the cameras (if viewing from inside).