Tobit speaks about two tithes (tenths) he gives in verses 7-8. His first tithe (Num 18.21-24), given to the Levites, is described in the second half of the first sentence in verse 7. A second tithe (Deut 14.22-29), given for a feast, is described in verses 7b-8.

I would give these to the priests: Priests may be difficult to translate in some languages, although in most languages the words or expressions which are most appropriate will already have been decided for the New Testament. A Handbook on Leviticus has an excellent discussion on the Levitical priests:

The primary duty of the priest was to serve as an intermediary between the LORD and his people. The means by which this was done was sacrifice. Thus in some languages this word has been translated “sacrificer” or “intermediary.” But care should be taken to avoid negative connotations of a word like “sacrifice.” If it evokes ideas of pagan sacrifice quite different from those of the people of Israel, then another term should be sought….

A Handbook on the Gospel of Mark lists terms that a number of cultures have used. Some examples are “one who presents man’s sacrifice to God,” “one who takes the name of the sacrifice,” and “spokesman of the people before God.”

The altar: In cultures where altars are unknown, we may say something like “place [or, platform] for sacrificing animals.” An alternative translation model for the first part of the verse is: “I would always take these offerings to the temple and give them to the priests at the altar” (Contemporary English Version).

The tenth of the grain, wine, olive oil, pomegranates, figs, and the rest of the fruits: This tenth refers to the tithe given to the Levites. Grain refers to crops of wheat and barley. Some translators will need to make this clear. For wine translators should not substitute something like “rice wine,” as the writer is referring to a fermented drink made from grapes. If wine is unknown in a particular culture, a translator may say something like “fermented drink made from the fruit called ‘grape,’ ” or simply transliterate the word wine and include a footnote explaining what wine is. Olive oil may be expressed as “oil made from the fruit called ‘olive.’ ” Pomegranates and figs, if not present in a culture, may be described in a similar way.

The sons of Levi refers to men from the priestly tribe of Levi who were not priests themselves, but who assisted the priests and took care of temple business that did not involve worship.

Also for six years I would save up a second tenth in money and go and distribute it in Jerusalem: Six years refers to the years between every seventh year (Good News Translation “Every year, except the seventh year”). Since the land was not to be farmed on the seventh year, no tithes were paid then; see Lev 25.1-7. A second tenth refers to the second tithe given by Tobit. For six years in a row he took an additional tenth and used it for a festive meal, as described in Deut 14.22-26.

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Tobit. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here.