Assuming the sales value is in A1 and the targert is in A3 then:
=A1*0.05 +MAX(A1-A3,0)*0.01+MAX(A1-1.2*A3,0)*0.02
it does give you the final result of 10600, do you need the internediate results as well.
The intemediate results are:
[TABLE="width: 316"]
<tbody>[TR]
[TD]=MIN(A3,A1)*0.05[/TD]
[/TR]
[TR]
[TD]=MAX(MIN(A$1,1.2*A3)-A3,0)*0.06[/TD]
[/TR]
[TR]
[TD]=(MAX(A1,1.2*A3)-1.2*A3)*0.08[/TD]
[/TR]
</tbody>[/TABLE]
Same assumption as before Sales value in A1 sales target in A3