You can box the divs by nesting another div like:
<style>
.resultCol {
float:left;
width:16%;
}
.resultCell {
box-style: border-box;
border: 1px solid black;
height: 22px;
}
</style>
<div id="results_wrapper">
<?php do { ?>
<div class="resultCol">
<div class="resultCell"><?php echo $row_RS1['serv'];?></div>
<div class="resultCell"><?php echo $row_RS1['serv1'];?></div>
<div class="resultCell"><?php echo $row_RS1['serv2'];?></div>
<div class="resultCell"><?php echo $row_RS1['serv'3];?></div>
<div class="resultCell"><?php echo $row_RS1['serv4'];?></div>
<div class="resultCell"><?php echo $row_RS1['serv5'];?></div>
</div>
<?php } while ($row_RS1 = mysql_fetch_assoc($RS1)); ?>
</div>