XSLT Grouping and Aggregation

This should be simple but I'm not very strong in XSLT.
I am trying to perform an XSLT on XML returned from a dataset that will give me the same
output as a "Group By" SQL statement combined with the "Sum" statement.

Using the Muenchian method i have been able to group by country but not Sum the Quantities

My XML Structure:

<?xml version="1.0" standalone="yes"?>
<NewDataSet>
  <Table>
    <ReportingDataId>2</ReportingDataId>
    <ReportingBusUnitDesc>United Kingdom</ReportingBusUnitDesc>
    <SystemQuantity>2</SystemQuantity>
    <TotalRevenue>10000</TotalRevenue>
  </Table>
  <Table>
      <ReportingDataId>2</ReportingDataId>
      <ReportingBusUnitDesc>United Kingdom</ReportingBusUnitDesc>
      <SystemQuantity>2</SystemQuantity>
      <TotalRevenue>10000</TotalRevenue>
  </Table>
  <Table>
      <ReportingDataId>2</ReportingDataId>
      <ReportingBusUnitDesc>Germany</ReportingBusUnitDesc>
      <SystemQuantity>4</SystemQuantity>
      <TotalRevenue>20000</TotalRevenue>
  </Table>
  <Table>
      <ReportingDataId>2</ReportingDataId>
      <ReportingBusUnitDesc>Germany</ReportingBusUnitDesc>
      <SystemQuantity>4</SystemQuantity>
      <TotalRevenue>20000</TotalRevenue>
  </Table>
</DataSet>

My XSL:
<?xml version="1.0" encoding="UTF-8" ?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform ">

  <xsl:key name="countryKey" match="Table" use="ReportingBusUnitDesc"/>

  <xsl:template match="/">
    <table border="0" cellpadding="0" cellspacing="0" width="1000">
      <tr>
        <td class="header">
          Country
        </td>
        <td class="header">
          units
        </td>
        <td class="header">
          revenue
        </td>
      </tr>
     
      <xsl:call-template name="dataTableGroup" />
      <!-- Sum the Totals of quantities and revenue-->
      <xsl:call-template name="dataTotals" />
    </table>
  </xsl:template>

  <xsl:template name="dataTableGroup">
    <xsl:for-each select="NewDataSet/Table[generate-id()=generate-id(key('countryKey',ReportingBusUnitDesc))]">
      <xsl:sort select="ReportingBusUnitDesc"/>

      <tr>
        <td class="columnTextRight">
          <xsl:value-of select="ReportingBusUnitDesc"/>
        </td>
        <td class="columnData">
          <xsl:value-of select="sum(SystemQuantity[../ReportingBusUnitDesc=current()])"/>
        </td>
        <td class="columnData">
          $
        </td>
      </tr>

    </xsl:for-each>
  </xsl:template>
 
  <xsl:template name="dataTotals">
    <tr>
      <td class="footer">
        Total
      </td>
      <td class="footer" >
        <xsl:value-of select="sum(/NewDataSet/Table/SystemQuantity)" />
      </td>
      <td class="footer">
        $<xsl:value-of select="sum(/NewDataSet/Table/TotalRevenue)" />
      </td>
    </tr>
  </xsl:template>
</xsl:stylesheet>

My desired output is:

Country                   Quantity       Revenue
Germany                     8               40000
United Kingdom           4               20000
Total                           12              60000

If anyone could set me on the right path I would be very greatful.