As far as I remember, not voting is punishable by a fine in my country, yet 15-20 per cent of the population does not vote.
I don't think the penalty will change the result, but the ease of voting and registration may help.

In fact, everyone who believes in democracy should vote because election day is the day when the voter makes a speech, the day when he/she raises his/her voice to the highest level. Whatever their preference, they should vote and have a say in the process afterwards.