It depends on exactly what you mean by paying out of your IRA. If you have the IRA custodian withhold tax from your IRA distribution then, yes, withholding is treated as having been paid evenly through the year, even if it's actually all withheld in December. But if you are taking money out of your IRA without having tax withheld, and you use some of the money that you took out of the IRA to make a tax payment, then it's just a payment that you make in December, and you would probably incur a penalty for not having paid during the year.
