Round to the nearest 10 in Excel or Open Office Calc

Is there a function, or does somebody have a formula or way of attacking these 3 problems, all in MS Excel (could also give an answer using Open Office Calc):  

(1) (a) How do you round to the nearest 10?  (b) Better yet, express the answer more generally.  So, the question, ideally, is, "How do you round to the nearest x, where x = a given, real number?"

(2) (a) How do you round up to the nearest 10?  (b) Same follow-up as in question (1).

(3) (a) How do you round down to the nearest 10?  (b) Same follow-up as in question (1).

I have Excel 2003.  I'd prefer an answer in Excel to one requiring Open Office Calc, but if there's a much easier way to do it in the latter, I'd be very interested in knowing that fact.  It will probably be easiest to follow this thread if people specify which problem they're addressing, for example, "Problem (2b)".

Thanks.