All aggregated numbers on the Dashboard are converted to a baseline currency. By default this baseline currency is set to your home currency.
You can change the baseline currency by clicking the settings icon in the lower right corner. This will bring you to the settings pane for the Dashboard.
In the Baseline currency section, you can change the baseline currency to any of the other currencies that you have accounts in. After the change, all aggregated numbers will be converted to the selected currency.