G-d told Moses to take two censuses of the Jewish people: one when he came down from Mount Sinai, and another when the Tabernacle was erected. In both cases, the male Jews age 20 and over were to be counted by having each one contribute a half-shekel coin. The silver from the first census was used to make the bases of the planks that made up the Tabernacle's walls. The silver collected from the second census was used to purchase the "communal" sacrifices, i.e., sacrifices offered up on behalf of the Jewish people as a whole. (In contrast, private sacrifices were purchased individually by the person offering them up).
[G-d told Moses,] " This is what everyone must give: a half-shekel; [specifically, half] of the shekel used for holy [purposes], which weighs 20 geirah."
Exodus 30:13
The half-shekel was an expression of Jewish unity--rich and poor alike gave the same amount. Everyone gave only half a shekel in order to teach us that we can only achieve unity when we all recognize that we are just halves. To be a complete shekel, we must unite with our fellow.
Similarly, we are also only "half" in our relationship with G-d. The ten powers of the soul--our intellect and emotions--parallel the ten powers that G-d used in creating the world and continues to use in order to constantly re-create it. When we channel all ten powers of our soul--every nuance of our being--towards uniting with G-d and fulfilling our Divine mission, we align our soul-powers with G-d's attributes. Our ten becomes twenty--a holy shekel.
From Daily Wisdom