Puts a sale sticker on, perhaps

• Marks up or down, say
• Puts new prices on, maybe
• Puts a sale price on, maybe
• Labels again
• Changes the price of, as at the supermarket
• Puts a new price on
• Changes the price on
• Corrects, as an ID on Facebook

Wiktionary Word definitions in Wiktionary
vb. (en-third-person singular of: retag )