This patch accomplishes this functionality. You don't have to collect the currency symbol, just save the value and format like with the php function “number_format” to get the value with the correct decimals.

Index: modules/Reports/ReportUtils.php
===================================================================
--- modules/Reports/ReportUtils.php     (revisión: 5892)
+++ modules/Reports/ReportUtils.php     (revisión: 5964)
@@ -75,11 +75,10 @@
                        $cur_sym_rate = getCurrencySymbolandCRate($currency_id);
                        if($value!='') {
                                $formattedCurrencyValue = CurrencyField::convertToUserFormat($currency_value, null, true);
-                               $fieldvalue = CurrencyField::appendCurrencySymbol($formattedCurrencyValue, $cur_sym_rate['symbol']);
+                               $fieldvalue = number_format($formattedCurrencyValue,2,'.','');
                        }
                } else {
-                       $currencyField = new CurrencyField($value);
-                       $fieldvalue = $currencyField->getDisplayValue();
+                       $fieldvalue = number_format($value,2,'.','');
                }

        } elseif ($dbField->name == "PurchaseOrder_Currency" || $dbField->name == "SalesOrder_Currency"