price on a penny

The 1905 penny would be British; Australian pennies didn't start until 1911. British 1905 pennies are fairly common; CV in the Krause catalogue is 50¢ in Fine, $4 in Very Fine.

The 1912 halfpenny is probably worth about the same, perhaps slightly more - I don't have a current Maccas or Renniks available handy at the moment, to give you current Australian prices.

According to the McDonald guidebook the current value of a 1912 half-penny is:
$1-00 V.G., $7-00 Fine, $30-00 V.F., $75-00 E.F.
Those amounts are in Australian dollars of course. Hope this helps!