The five include leaders of the Democratic Front coalition and a representative of the New Rightists party.
They began their protest shortly after an estimated 3,000 market traders demonstrated in front of the parliament building in Tbilisi.
In a bid to curb tax evasion, the government has made cash registers mandatory at all markets since March 1. It has threatened impose heavy fines on traders who fail to do so. Traders want expensive cash registers to be replaced with a monthly tax.
Meanwhile, hundreds of traders have gathered in front of the parliament building in Tbilisi in protest.
An estimated 3,000 market traders staged a similar demonstration on March 9, but Prime Minister Zurab Noghaideli has ruled out any discussion with the protesters.
(Imedi TV, Civil Georgia, Novosti-Gruziya)