Hey Christie,
It really depends on who you are sending the emails to. If its to your current customers anything over 1% is not ideal, but if they are it could be a case that your customer database is old and some customers may now be using a new email address.
If you click on a bounced email and then go into Lead Info, you will fiund a field called "Email Invalid Cause" this will give you an idea of why they bounced. So might be worthwhile exporting out all your bounced emails and filter through that field and you will see where the majority of bounces happed.
If its bouncing because of spam....you could have yourself a few issues in the future whereby mailservers will blacklist your company email as spam. In this case you might want to try and see if you can spam score your mails before you send them out. This can be done using the IBM deliverabilty tool if you use that or there are some less accurate but still useful websites online that can help you do this and give pointers on where you might be at a high risk of spam!
http://www.contactology.com/check_mqs.php
Hopefully this has been useful.
Regards,
Barry