Create your own tab in system configuration in magento

Create a new module in your local folder, add etc directory to the module and create system.xml with the following content -:

<config>
    <tabs>
        <scommerce translate="label">
            <label>Scommerce Configuration</label>
            <sort_order>10</sort_order>
        </iredeem>
    </tabs>
</config>

You can add sections in your newly created tab by adding normal system configuration entries in the same system.xml

<config>
    <tabs>
        <scommerce translate="label">
            <label>Scommerce Configuration</label>
            <sort_order>10</sort_order>
        </iredeem>
    </tabs>
    <sections>
        <scommerce_tracking translate="label">
            <label>Tracking</label>
            <tab>scommerce</tab>
            <sort_order>10</sort_order>
            <frontend_type>text</frontend_type>
            <show_in_default>1</show_in_default>
            <show_in_website>1</show_in_website>
            <show_in_store>1</show_in_store>
            <groups>
               .......
            </groups>
    </sections>
</config>

Make sure you create your module.xml file in etc/modules directory to enable your module