I believe the IRS treats bitcoins as property, rather than an actual currency. But form what I've heard, when doing you're taxes, you actually just treat it as regular payroll taxes.
March 31: 25BTC (price per BTC - $200) June 30: 20BTC (price per BTC - $250) September 30: 20BTC (price per BTC - $250) December 31: 10BTC (price per BTC - $500) Total: 75BTC
Now at the end of the year you need to calculate your income. You made 75BTC over the year, each of which was purchased at a different price. When you sell them to transfer them into USD, you need to keep track of _which_ bitcoin you are selling. If you sell one on December 31st, was it one from your first paycheck (in which case you made a profit of $300, which counts as income because you didn't hold it for over a year) or from the last one?
Simply buying BTC with USD from a company's bank account and sending it somewhere isn't difficult. To actually provide a service that doesn't leave employees in a tax nightmare they have no way of understanding is really what matters.
http://www.irs.gov/uac/Newsroom/IRS-Virtual-Currency-Guidanc...