"display: inline-block" used to be outside the ePub 2 specification, and not supported by some readers. I don't know what's the status now, but I wouldn't rely on it.
My preferred (possibly outdated) solutions:
In English: . . . (adding extra on the side depending on the surrounding punctuation.)
In Spanish: ... (because that's the correct typesetting of an ellipsis in Spanish, got to love its simplicity
)