I would not say "Wieviel ist das?". That sounds wrong to me. Ich sage: "Wieviel macht es?" oder "Wieviel macht es aus?" (When there's something to add up. When you bought eggs and milk and sugar, at the end you can ask: "Wieviel macht es aus?" (in Summe, in total) If I buy only one specific piece (1 Hose, 1 Brot), I usually ask: "Wieviel kostet das?" But that's not a fixed rule. Just my habit here.

Yes, you can ask 'wie viel ist das?'