If you want to round to the nearest whole number
=ROUND(A1,0)
Your subject line talks of rounding to 0 or 0.5, for which one option is
=MROUND(A1,0.5), but you'll need the Analysis ToolPak Add-In for that, or
else you could use =ROUND(A1*2,0)/2.
Not following you 100% as bot of your examples are rounding up to the nearest
whole number (noting to do with 0.5) ...but here is a formula to round to the
nearest .5