pay.jp 'rounds up' the order total price instead of 'round off'

I have my tax calculation and order value calculation set to 'round off' in settings.
When my total order price is in decimals, it should get round off to the nearest lower integer. On order summary page, it calculates the final order price correctly by rounding off the values, but cuts 1 extra yen from a customers' bill and my client has to return that yen to that customer, every time he/she selects pay.jp as a payment option.
I debugged this a little and found out that the formatNumber function in payjp.php file uses php function
"number_format" which ends up rounding off the total order price.
I'll create a patch with alternate use of function round() and upload in a while.