I am a former tax cpa. When I first started out, I noticed that almost every client of ours had a $499 charitable deduction (in addition to actual cash they gave to church). So our CPA must have decided that $499 was a "safe" amount. However, the actual formula for deciding audits is secret, and no one can actually tell you the answer (it's best guesses). Always get a receipt when donating. If you don't have proof and you are audited (very low risk), then you will have to pay back taxes and interest on that amount.
