I'll try to answer a bit more generally. In a language that has declension classes, or different ways to form the plural, it is to be expected that nouns occasionally show variation in how they form the plural, and they may eventually change their declension class. New High German uses the plural endings ‑e, ‑n, ‑er, ‑s and no ending (Nullplural in German).
When a new plural form is introduced, there are three possible outcomes:
The new ending does not take root and the old one persists. Example: The form Stiefeln (suffix ‑n) appeared and went out of fashion again, older Stiefel (Nullplural) persisted.
The new ending takes over, the old one dies out. Example: Helde (suffix ‑e) was replaced by Helden (suffix ‑en).
Both endings persist. Usually, one of the forms will be perceived as more old-fashioned or poetical than the other. For instance, Goethe uses Sinnen (suffix ‑en) instead of Sinne (suffix ‑e): Ha! welche Wonne fließt in diesem Blick / Auf einmal mir durch alle meine Sinnen!
Alternatively, the forms take on different meanings. The standard example of this is Worte (‑e) versus Wörter (‑er): The former designates words in connected speech only, whereas the latter sees words as something that is counted or alphabetised.
Now it is a matter of judgement whether you want to subsume Tale under 2. (a form that died out again) or 3. (a form that exists but is perceived as old-fashioned or poetical).
Finally, note that Middle High German tal had Nullplural (Luther still uses Tal as plural). However, nouns like tal eventually lost this possibility and developed plural forms ending in ‑e or ‑er. This development has been a source of nouns that have two ways to form the plural. Sometimes, both forms have persisted, and, in accordance with 3. above, taken on different meanings. Some examples: Lande, Länder; Bande, Bänder; Denkmale, Grabmäler; Tuche, Tücher; Worte, Wörter. These are taken from Hermann Paul's Deutsche Grammatik, II, § 21 (see here).
Some references for variation between ‑e and ‑n are in my answer to Was ist der Plural von “Forst” (in German).