I suspect you'll find cutting tape to be more trouble than it's worth.
Remember that every time you coverslip a slide you're, in effect, completing
the assembly of the microscope objectives in use on all the microscopes in
your lab.  So while coverslipping is tedious, it's nonetheless important.
As Tim mentioned, histo sections are more tolerant of tape than are (thick)
cyto slides.  Low power objectives such as 4X and 10X are insensitive to
glass/tape thickness, refractive index, dispersion values, and
planoparallelism deviations from specs.  (Specifically, it is the numerical
aperture that is determinant.)  Also, high quality objectives are even more
unforgiving (e.g., apochromats vs. achromats).  40X achromats begin to show
fall-off in image quality when the combined thickness of cover glass and
mounting deviates +/- 15 micrometers from 180 micrometers thickness.  Again,
and finally, however, all the benefits of proper coverslipping will be
masked by non-Kohler illumination (e.g., substage condenser aperture
diaphragm wide open), pale staining, dirty lens surfaces, dirty eyeglasses,
etc.  Microscopy is enjoyable.  Why compromise quality by using non-standard
materials?  If you like tape, you'll love liquid substitutes for cover
glasses.

Gary Gill