<- Nebraska native here.
Yes, Iowa is usually a bit cheaper on the gas. I usually see Iowa being 10 cents cheaper per gallon.
Current averages: Iowa $2.933, Nebraska $3.049. So right now it is about 12 cents cheaper in Iowa.
What I think got saw was a dramatic increase in gas prices. Gas earlier in the week in Lincoln Nebraska was $2.79/gallon. Gas today on my way to work was $3.04/gallon at the same stations. Things went up 25 cents in the last couple of days. So, earlier on your trip you got the cheap price (in Iowa and Illinois), and later (while in Nebraska) you got the expensive price.
Most stations around here have three prices: regular, midgrade, and premium. But, if a station only has a sign with two prices, 99% of the time it doesn't show the regular price. The regular price has been ~10 cents more expensive for several years at all gas stations that I've seen in Nebraska. So, just add 10 cents to what you see. I'm not bothered since all stations do this, and you have to fill up, so the lack of a regular price on the sign it is not important at all.
Finally, I've seen many people insist that all 3 grades are 10% ethanol, but that only one sticker is on the pumps. There have been many debates about this on Anandtech threads. They argue that you are delusional thinking it was the one under the sticker that gave you problems when ALL grades had ethanol. They argue that the law is "one sticker for three pumps". They argue that the refineries and trucks don't have 3 types, but only two (1) regular with ethanol and (2) premium with ethanol. The midgrade is just a blend fo the two. However, I haven't actually been able to find any documents or links yet that prove one side or the other. Can anyone in this thread help clarify?