Tithes in the Old Testament were primarily taxes for funding the national budget in Israel. Since Israel was a theocracy, the Levitical priests acted as the civil government. So the Levite's tithe (Leviticus 27:30-33) was a forerunner to today's income tax in which they tithed grain, new wine, olive oil, and the firstborn of their herds and flocks. If the distance was too far for them to carry the tithe, then they were to exchange their tithe for silver, and take the silver with them and go to the place the Lord chose and use the silver to buy whatever they like: cattle, sheep, wine or other fermented drink, or anything they wish. (Deuteronomy 14:22-29). Smaller taxes were also imposed on the people by the law (Leviticus 19:9-10; Exodus 23:10-11). So the total giving required of the Israelites was not merely 10 percent, but over 20 percent, which is similar to our taxation system today. All that money was used to operate the nation.
All giving apart from that required to run the government was voluntary (Exodus 25:2; 1 Chronicles 29:9). Each person gave whatever was in his heart to give and no specific percentage or amount was specified. In the Church age under the New Covenant, believers are never commanded to tithe 10%. Matthew 22:15-22 and Romans 13:1-7 tell us about required giving, which is the paying of taxes to the government. We in America presently pay between 20 and 30 percent of our income to the government, which is a figure very similar to the requirement under the theocracy of Israel under the Old Covenant
Now if someone wants to give 10% of their income or more to their church or another Christian organization, that is fine, we cannot out give God, yet we should not turn the 10% tithe for Israel under the law into a legalistic prescription for Christians under grace. Now just because a specific % is not listed under the New Covenant for Christians to give, this does not mean we should give grudgingly either.