eCart wont support showing the danish currency symbol, but you can make sure it is passed to paypal as dkk by editing the paypal code.
for PayPal payments pro, the following code on the confirm page will set the curency;
$PP_DirectPayment_required[0][$nextIndex] = "Currency";
$PP_DirectPayment_required[1][$nextIndex] = "USD";
you could change that to:
$PP_DirectPayment_required[0][$nextIndex] = "Currency";
$PP_DirectPayment_required[1][$nextIndex] = "DKK";
to have the currency sent to paypal set to dkk.