The only calculator approved for this course is the Texas Instruments TI-30Xa

This one was bought at Wal-Mart April 12, 2003 for ten dollars. In August 2003 they were selling various Texas Instruments calculators, including this one, for the same price of $18. Since this one is the simplest of them all, it is not a good deal any more.

The above picture shows the battery version, which is the cheapest of them.  The variants, that are also allowed are the solar and ecological versions:

Do not confuse these approved versions with TI-30 II (with a two-line display), which is not allowed. It is also about twice as expensive.