the Wikipedia link you gave says: exposure of a person repeatedly touching thermal printer paper for 10 h/day, such as at a cash register, could reach 71 microg/day, which is 42 times less than the present tolerable daily intake (TDI).
Present being the operative word. Plus cashiers don't rub the receipts against their hand for long periods of time building up sweat, as you might if you were filling out a puzzle.
Anyway I did say potential, but as the researcher suggests pregnant women working as cashiers should be careful and err on the side of caution.
