With the help of the Russian army Transnistria was quick to claim victory, disconnecting the region from the rest of Moldova for generations to come. In fact its status as a country is still open to debate. Having its own government, currency, constitution, police, secret police , central bank, border checkpoints and national anthem, one could argue though that Transnistria is a country.
I met two other travellers who did not prepare for this, so they spent a couple of hours driving around by taxi looking for an ATM that worked. Also keep in mind that Transnistria is one of the poorest regions in Europe so you are very unlikely to spend much.
Be aware of what you photograph, as some things are not meant to be shared to the outside world. I found this out the hard way and got arrested by the KGB. One tip is to either speak the Russian language yourself or to have a phone number of preferably a local who does, just in case you run into problems.
If you want to stay overnight you should register with the local police. Finding out where to go is very difficult though, and also expect zero English skills from officials. Keep in mind you need to wear long trousers if you want to get in the office, it is mandatory.
You should also learn how to read Cyrillic. If you stay in a hotel, the hotel will register you but if you choose to rent an apartment yourself or go Couchsurfing you need to do it yourself. It is very wise to bring a local with you. Staying overnight brings me to my last comment for travellers: in Tiraspol there are no more backpacker hostels.
