No way to use a slot for 1%! But that 1% is often the decisive factor to use 1pt of mana less in your special move or spell (take lightning strike for example, with 39lmc you need 7 mana with 40lmc you need 6). So in general it does not realy matter. If you have a tweaked template and you want to squeeze out three special moves in a row, it can make all the difference.