master.xml

<data>
  <entry>Text</entry>
  <entry>Text</entry>
  <entry>Text</entry>
  <entry>Text</entry>
  <entry>Text</entry>
  <entry>Text</entry>
  <entry>Text</entry>
  <entry>Text</entry>
  <entry>Text</entry>
  <entry>Text</entry>
</data>

master.xsl

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">

  <xsl:output method="xml" indent="yes" />

  <xsl:template match="/">
    
    <h2>What i get:</h2>
    
    <xsl:for-each select="data/entry">
      	<xsl:choose>
     	 <xsl:if test="position() mod 4 = 0">
        every 4th!
    	</xsl:if>
      <xsl:otherwise>
        normal
      </xsl:otherwise>
      </xsl:choose>
    </xsl:for-each>
    
    <h2>What i need:</h2>
    
    <div>Text</div>
    <div>Text</div>
    <div>Text</div>
    <div class="last">Text</div>
    <div>Text</div>
    <div>Text</div>
    <div>Text</div>
    <div class="last">Text</div>
    <div>Text</div>
    <div>Text</div>
          
  </xsl:template>

</xsl:stylesheet>