In my spreadsheets, when I choose a 2-decimal-place currency format, quite frequently recently, trailing zeros are simply dropped in new entries (if they're in existing entries, they seem to stay). They show up again if I go back to Format and rechoose 2 decimal places, but I shouldn't have to.

As an example, a new column of numbers I add appears as:

$5.5

$6.27

$19

Instead of 

$5.50

$6.27

$19.00

This started happening a few months ago, just haven't asked about it until now.