This is definitely the uniform of the New South Wales Militia Infantry - the white collar tabs are quite distinctive. The uniform was worn from about 1895 (when New South Wales was a separate colony with its own military), until a few years after Australian federation.
From the detail of the uniform, he was probably a member of the 1st, 2nd, 3rd or 4th NSW Infantry Regiments. These were all Militia units, based in Australia - NSW units actually serving in South Africa during the Boer War wore different uniforms from this.