Although it IS customary to 'tip' in Egypt, most visitors (tourists) go way OTT and tip far too much, which is damaging as it then creates a culture of 'expectancy', with every man and his dog expecting a big fat tip from every tourist they encounter, for providing no kind of 'service' at all, so don't fall into that trap.
Tips should be kept 'in proportion', with a menial service (carrying your bags to your room) getting a tip of 1 or 2LE.
A room cleaner should perhaps get 2 or 3LE per day (20LE for the week) and a driver perhaps 5LE for a long journey, or 1 or 2LE for a shorter journey.
A guide perhaps 10 or 20LE for the day, but ONLY if you are happy with the service provided. These may not equate to large amounts in your own currency, but again it is keeping things in proportion, as 100LE is a weeks wages for many in Egypt and I doubt if you would tip anybody a weeks wages in the UK, would you.
The other factor with 'over-tipping' is that word soon gets around that you are an 'easy touch' and you will be hounded and hassled everywhere you go and this could potentially ruin your holiday, so be warned !