title: Tablix row sum by one column value
body: <p>I have a tablix with two columns. One is for tax rate (0%, 5%, 10%... - <code>=Fields!TaxRate.Value</code>), other for total tax values (<code>=Fields!TotalTax.Value</code>).</p>
  
  <p>In my report I receive these values as:</p>
  
  <ol>
  <li>Tax rate 20%  -  $500</li>
  <li>Tax rate 5%  -  $20</li>
  <li>Tax rate 20% - $450</li>
  <li>Tax rate 5% - $25</li>
  </ol>
  
  <p>How can I put all the same tax rates in one row and sum up the values, by same tax rate, such that the result is:</p>
  
  <ol>
  <li>Tax rate 20%  - $950</li>
  <li>Tax rate 5%  - $45</li>
  </ol>