Not officially IIRC as there doesn't officially seem to be any sort of app available out there for storing USDT on a Ledger, but USDT is now available on the Ethereum blockchain as an ERC20 token and you should be able to store your USDT using your Ledger device and MyEtherWallet as MEW allows you to unlock your wallet with a number of hardware wallets like Ledger, Trezor and KeepKey as well. I've only ever used MEW with an old privkey and I haven't used any of my hardware wallets with them before, but I only see positive things around about MEW's compatibility with hardware wallets.