It's possible, but i wouldn't recommand buying $5 from anywhere... There are a couple of reasons:
1) you'll pay a hefty premium
2) the seller will pay a hefty fee (and pass this price on to you)
3) you'll start gathering dust outputs, so you'll have to pay a big fee if you want to spend those again.
At this moment,
https://bitcoinfees.21.co/ tells me that at current BTC price, you'll have to pay more than $1,5 fee for an average sized (226 byte) transaction if you want a decent chance of getting a confirmation in less than an hour...
It breaks my heart to say this, but if you're dealing in micro payments, it might be a better idear to switch to an altcoin instead...
And pop goes the bubble...
This is what I feared. I suppose I have to weigh the novelty of buying $5 in btc vs the reality of buying $5 in btc.
I'm afraid so... If you buy $5 worth of btc, i'd be supprised if you could use your $5 to buy a $2,5 item using your BTC... At this point in time, i suppose you'd lose more than 50% in premium and miner's fees...
Don't worry tough: i'm confident that in a little while, a scaling sollution will popup, and i hope the fees will go down as a result of this (no guarantee tough, just an educated guess). It's just the wrong moment to start experimenting with micro payments and BTC.
Like I said: it breaks my heart to say this, but for micropayments, you might be better off using altcoins... I'm not really into altcoins, but if you picks an old, stable one with a good reputation, it should work for smaller payments...
A client of mine instisted in paying in ETH just this week, payed me 0.75 ETH, looked like an ordinary, small transaction, payed 8 cents in ETH fee...