I sell outside India. How do I set tax?

Use your own country's tax (VAT in the UK/EU/UAE, sales tax in the US). Go to Settings → Store Settings → Manage Tax, click Tax Settings, tick Enable tax on this store, set the Default Tax Label (e.g. "VAT") and click Save Settings. Then add your rate with the right Country (and State if needed) and click Add rate — the Country list shows the countries you've added under Settings → Store Settings → Selling Location. If you aren't registered, leave tax switched off — it is off by default.