What about using a different style for your last post? Let's imagine that you have this code currently:
<?php if (have_posts()) : ?>
<?php while (have_posts()) : the_post; ?>
<div class="post">
my post content
<div class="divider"> </div>
</div>
<?php endwhile; ?>
and that you limit your post numbers per page to 5. Considering this you could set-up your code like this instead:
<?php if (have_posts()) : ?>
<?php while (have_posts()) : the_post; ?>
<?php $postclass = ($post == $posts[5]) ? 'entry-5' : 'entry'; ?>
<div class="<?php echo $postclass; ?>">
my post content
<div class="divider"> </div>
</div>
<?php endwhile; ?>
The results should be that posts 1 thru 4 will use "entry" as their class, while post 5 would use "entry-5". Then yor stylesheet could use something like this:
.entry-5 .divider { display:none; }
I haven't actually tried this myself, however a post I was reading here is where the thought originated from.
Hope this helps.