Sample Package.xml:
<?xml version=”1.0″ encoding=”UTF-8″?>
<Package xmlns=”http://soap.sforce.com/2006/04/metadata”>
<types>
<members>Listing__c</members>
<name>CustomTab</name>
</types>
<version>30.0</version>
</Package>
<?xml version=”1.0″ encoding=”UTF-8″?>
<Package xmlns=”http://soap.sforce.com/2006/04/metadata”>
<types>
<members>Listing__c</members>
<name>CustomTab</name>
</types>
<version>30.0</version>
</Package>
CustomTab is also used for fetching Web Tab and Visualforce Tab.
Cheers!!!