Ausschreibung = a solicitation to bid for a set of services/work
Ausschreibungen = the plural version
..in german legal documents. For example in the field of architecture when a company is accepting bids for a new construction. German is not like English where you can just attach an "s" at the end to make it plural. The only public reported sales for the base of this term are as follows:
ausschreibung.net €460
ausschreibungen.eu €240
e-ausschreibung.de €180
As you can see, it is either "ausschreibung" or "ausschreibungen" contained in the few reported, small sales. Either ausschreibung.com or ausschreibungen.com would be a great domain, but not ausschreibungs.com. Furthermore, here are the exact search scores which should help clarify how popular each exact term is:
ausschreibung: 5,400
ausschreibungen: 6,600
ausschreibungs: 20
sorry but the non-word ausschreibungs appears to have little or no value.