help with excel formula

[dvjrcj2]

I need help with a formula for a spreadsheet i am working on. I need the formula for:
ex: d1-d2-d3-d3= x and if d2 contains a value then divide x by 2.

also, how do i round up to the nearest 5 and have linked formulas reflect the rounded #?

Thanks so much!

 

[dvjrcj2]

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