Yes, you can. If you've sent an offer and the owner hasn't responded to it yet, you can cancel without penalty or further action.
If you cancel after an offer is accepted and you've reserved the property, however, you may lose some or all of your deposit. The owner has taken their listing off the market and reserved it for you successfully. If you decide to back out anytime afterwards, the owner has essentially gone through this entire process for nothing. In that time, they could have gotten more exposure for their listing or even received more offers.