I had immense problems with a Tesco Matercard in more than one place just this year.
Fag shop in Adinkerke twice
Restaurant in Place du Jacobin twice in two days
Petrol station in Carrefour Le Mans (booth not pump)
Hotel in Frankfurt
They often end up with "no authorisation", so I give them another card to use.
I don't suspect the retailers. Tesco have been really annoying. If your card appears somewhere "unexpected" then they request the transaction be authorised by phone.
Most retailers can't be arsed and simply say "card rejected have you got another".
A few times Tesco have been on the mobile within seconds of the failed transaction to ask where I am. Which I suppose is commendable from a security viewpoint but a pain when you are trying to shop.
So I call then before going away and tell them to expect transactions from these countries...
Thank you, they say, but that doesn't mean we will allow all transactions. Doh...
I tried renewing my domain name with my US provider by phone using that card. Twice it got rejected so in the end I used another. I called Tesco to ask them whet's up, they said an authority had been given. The retailer didn't get it though...Of course, I now have three identical payments to the US company which will cost me time and money to sort out...
I am going to stop using Tesco Mastercard abroad...
Having said all that, back to the original question - the tolls always take whatever I throw at them. They don't even have time to validate. I suspect they work on the law of averages - if they get the occasional dud then it's not a biggie for them...