Square wave on tape

[Doyle]

I recently bought  a fairly good quality rotel tape deck for $10 at the
tip. It has all the usual features (L/R mike, Dolby NR, Bias, EQ, counter
and VU meters..)
It doesn't sound too good on my HiFi system (which had no line in until I
added a socket attatched to the tape head), probably because of the
impedence..
ANYWAY....I decided I'd test out my Multimeter's Hz measuring and check out
the deck at the same time....so i plugged in frequencies to the input,
measuring them..this turned out fine...a little weak in the top area, but
acceptable...
SO THEN i thougt i test the distortion, so out goes the multimeter and in
goes the scope...
everything's fine until  i display the result of a recorded square
wave...this was no longer square, it was a sine wave's interpretation of a
square wave, quite smooth in fact...
QUESTION: ((at last!) is it possible to record a square wave onto magnetic
tape?