It's possible, but it's not natively supported. It would require you to make core changes, which will be overridden during upgrades. You would need to maintain the changes in your installation.
Amounts are displayed in several places across the admin/client interfaces, but for brevity I'll give an example of one place on the Wizard order form. The other order forms (i.e. Standard/AJAX) would need to be updated similarly.
This example will change the price display on the Wizard order form's drop-down menu for Term and Price. This will show prices using the per-month price rather than the price for all months combined.
Open /plugins/order/views/templates/wizard/config.pdt
Find (line 37):
$prices[$price->id] = $this->_("Config.index.package_price", true, $period, $this->CurrencyFormat->format($price->price, $price->currency));
Replace with:
$amount = $price->price;
if ($price->period == "month" && $price->term > 0)
$amount = ($price->price/$price->term);
$prices[$price->id] = $this->_("Config.index.package_price", true, $period, $this->CurrencyFormat->format($amount, $price->currency));