This is a _terrible_ idea. If voters walk out of the voting booth with a receipt that says how they voted, you've just enabled everyone who might want to pressure, bribe, or influence voters. Domineering husbands will demand that their cowed wives vote the "right" way, and then offer proof of it when they get home. Employers will give bonuses to employees who proove they voted a certain way. Religious figures will deny services to people who voted "wrong". In areas with a poor police presence, gangs will demand to see your receipt and beat you up if you can't prove you voted the way they want.
It's a deliberate feature of our voting system that after you leave the voting booth, there is no way that anyone can gain knowledge of how you voted. This enables people to vote their concience. It makes it almost impossible to harass or reward someone based on how they voted. To change this would be a disaster.