We have a business customer who regularly writes a check from their account and deposits it to their account at another bank. The dollar amounts of the checks are weird though. For example:

$11,111.11
$9,999.99
$8,888.88
7,777.77

We have not yet asked the customer about them. But at first glance, do you think this indicates something that would prompt us to file a SAR? I can't think of anything, but it sure does look strange.

following...we dont have business account but i am curious on opinions

You are going to need to ask your customer about this. It does look unusual though.

If these are self-to-self checks, not from business to personal or business to business or anything else that might obscure ownership, and there's no concern about the source of funds, I probably wouldn't spend much time on it myself.

i'm trying to see the basis for a SAR here, "the customer is writing checks for weird amounts" just doesn't seem like a good reason. yes, query the customer, then file or not and move on.

There is not enough information:
how often?
What did the customer say when you asked? yes that is necssary