The answer depends on what you are using the <div>
for. If you are using it to define a section of text that is styled differently than your "normal" paragraphs, then yes, you can certainly add styling to the div to make that section "stand out".
Code:
p {whatever styling you want for normal paragraphs (98% of the book)}
div.newsarticle {margin:2em - or whatever you want for the div box itself}
div.newsarticle p {whatever special styling you want for paragraphs within the div}
div.newsarticle p.head {whatever styling you want for news article headers}
<body>
<p>This is a normal paragraph.</p>
<p>This is a normal paragraph.</p>
<p>This is a normal paragraph.</p>
<div class="newsarticle">
<p class="head">Heading</p>
<p>This is a news paragraph.</p>
<p>This is a news paragraph.</p>
<p>This is a news paragraph.</p>
</div>
<p>This is a normal paragraph.</p>
<p>This is a normal paragraph.</p>
<p>This is a normal paragraph.</p>
</body>
If, however, you are making the uncultured, uncouth, barbaric, decision to use a <div> to wrap your paragraphs instead of using the paragraph tag <p>, then, first, you need to rethink that approach - use the actual tag designed for the purpose, and second - refer to the first reason!, and third, slap yourself for skipping the first and second reasons and just use the actual tags as they are intended.
Having said all that - I agree with not defining margins for normal paragraphs at all and let the device define the standard margin.