I like this idea tho the spikes and falls of BTC against local fiat currencies, currently, does not allow for fixed pricing.
I wonder... if you put BTC price tags on everything and prohibited returns, but fixed the exchange rate at your store to somewhere above market like $1250 USD/BTC. So if people wanted to pay fiat for an item you price at BTC0.5 (that you bought wholesale for the equivalent of BTC0.25 at $240 USD/BTC), they'd have to pay $625 USD.