Should I change my rDNS entries?

(I wasn’t entirely sure which category to post in but this seemed the most appropriate)

I have a server with the rDNS set to my hostname for the main IP address. I also have a number of additional IP addresses, one for each site that uses SSL, and each of these has a different (seemingly random) rDNS, that I didn’t set.

My question is: should I change the rDNS for these and if so, to what? The hostname of the server or the domain name of the individual site?