Rounding To Specific Numbers

I am looking to round numbers to specific values 2, 4 and 6.

I was thinking of a code in a query something like:

if <3 but >0 then 2
if <5 but >3 then 4
if >5 then 6

can anybody convert this into queery code, not SQL tho because I'm rubbish at that. I just want to type it into the criteria on my field box on the query.

I also just tried to do it with:

IIf(>0 And <3,2,IIf(>3 And <5,4,IIf(>5,6,IIf(0,0))))

but this only seems to return results of 4 and doesn't show all entries, like entries with no value entered. I also think i'm missing out the numbers 3 and 5 because it's less than and greater than but not the number itself:
if 5 or < or > (to include the 5)

thanks

Ok I've now got
IIf(<1,0,IIf(>1 And <3,2,IIf(>3 And <5,4,IIf(>5,6,IIf(0,0)))))

which I think is doing roughly what I need but i have stumbled on a new problem.

These results are based on the average result of another query but i need to add a section before the results are averaged that says

if(=0 or no entry then all results are 0 for that unit else avg but iif(<1 etc. (the original statement above)

Thanks for your help