Its not possible to just do this with plain svn. As it defeats the purpose of a centralized version control.
However svk(with svn) will be a best fit for your need. svk is a decentralized version control system(it wraps svn).
From svk's FAQ
<snip>
* Does svk allow you to make several commits to your local copy of the repository and then be able to merge all the commits back to the main repository (keeping all the log messages)?
Yes - this was its very first feature. However the merge of local changes will be one commit in the remote repository by default, unless you use smerge -I. Meanwhile, smerge -l will bring the logs to the commit made to remote repository.
</snip>