According to Wikipedia,
The last two sins (repetitions of the letter תּ) are "תָּעִינוּ
תִּעְתָּעְנוּ" (taw'inu, titawnu) are usually translated as: "We went
astray, We led others astray". Occasionally the last word is
translated as "You (= the Deity) allowed us to go astray"—the widely
used ArtScroll Siddur uses both possibilities,[3] the point being that
the last word is an unusual form (not found in the Bible) that
suggests a positive determination to go astray, the misuse of free
will.[4] However, the translation of "You let us go astray" has been
criticized as an error, and it has been suggested that the last word
means "we have scoffed" or "we have mocked" or "we tricked" or "we
misled others".[5]
See notes there. In addition, see this discussion which notes that Artscroll changed its translation:
The Artscroll Siddur (1984 edition) correctly translates Ti'ta'nu as
"we
have led others astray" using the verb letataya as it is used in the
passuk "vehayiti be'einav k'metataya" ([...] as a trickster).
However in the Artscroll Yom Kippur Machzor (1986) and the Artscroll
Selichot (1992) the word is translated as "You have let us go astray"
which seems incorrect... Not necessarily incorrect. It follows the translation in the Chayei Adam. "You have left us to our free choice to stray".
In other words, later editions of Artscroll follow the interpretation of the Hayei Adam who maintains that תעתענו means that God has allowed us to stray (because of our previous sins), however, the simpler interpretation of the word is that it refers to our own sin (of causing others to stray or of scoffing, etc.). Rabbi Jonathan Sacks, in his machzor, translates this as "we have led others astray."