Writing IF Function

[Jabbaman]

Hi,

I,am wanting to write a function so that in cell B2 it will start at $10 and automatically add $5 until cell D gets a number 1
At the moment i have =IF(D2<=1,10,IF(D2>=1,10+5))
Cell E is what it should be, I have attached an example, I hope someone can help. Thanks