Olhando para obter o XPath de US $ 2,00 com este bloco:

<td class="undefined" colspan="6">
   <table class="history-bill-payments" cellspacing="0" cellpadding="0" border="0" align="center" width="99%">
<thead>
<tbody>
   <tr>
      <td valign="top">04/19/2016</td>
      <td valign="top" style="text-align:right; height:">
         $3.00
         <br/>
         $2.00
      </td>

Eu tentei estes, mas sem sucesso

$I->CanSeeElement("//table[contains(tbody/tr[2]/td/table/tbody/tr/td[2]/following-sibling::br)]"); 
$I->CanSeeElement("//table[contains(tbody/tr[2]/td/table/tbody/tr/td[2]/preceding-sibling::br/text(),'$2.00')]"); 
$I->CanSeeElement("//table[contains(tbody/tr[2]/td/table/tbody/tr/td[2]/following-sibling::br/text(),'$2.00')]");

Usando firepath no Firefox eu recebo este XPath

html / body / div [4] / div [2] / div / div / div / div / tabela / tbody / tr [2] / td / tabela / tbody / tr / td [2]

Consegui obter o xpath de US $ 3,00

$I->CanSeeElement("//table[contains(tbody/tr[2]/td/table/tbody/tr/td[2]/text(),'$3.00')]");