Here's the statute:
Mississippi Code Annotated section 13-5-34 (Punishment for failure to appear)
(1) A person summoned for jury service who fails to appear or to complete jury service as directed, and who has failed to obtain a postponement in compliance with the provisions for requesting a postponement, or who fails to appear on the date set pursuant to Section 13-5-33, may be ordered by the court to appear and show cause for failure to comply with the summons. If the juror fails to show good cause for noncompliance with the summons, the juror may be held in civil contempt of court and may be fined not more than Five Hundred Dollars ($500.00) or imprisoned not more than three (3) days, or both. The prospective juror may be excused from paying sanctions for good cause shown or in the interest of justice.
(2) In addition to, or in lieu of, the fine or imprisonment provided in subsection (1) of this section, the court may order that the prospective juror complete a period of community service for a period no less than if the prospective juror would have completed jury service, and provide proof of completion of this community service to the court.
As for how likely it is that you would actually have to face some kind of penalty, I have no idea. Courts routinely summon significantly more people than necessary for jury duty because that's the only way they can be sure to fill a jury after some people get excused by the lawyers for one reason or another.
Slightly fun fact: The following people are automatically disqualified for service on a jury...
-anyone convicted of an "infamous" crime
-anyone who has been convicted of the "unlawful sale of intoxicating liquors within a period of five years"
-"common gambler" (I guess uncommon gamblers are ok)
-"habitual drunkard"
