這樣應該是比較禮貌的說法:

一共是XX元!
That would be xxx dollars.

收您XX元！
xxx dollars from you.

找您XX元!
Here's your change, xxx dollars.

您的發票!
Here's your receipt.

需要微波嗎?
Would you like to have it microwaved. (可以這樣用嗎 )

小心燙手!
Watch out, it's pretty hot.