Sorry just had to pipe in.
I've yet to meet a Micro designer that doesn't like to use the smallest PIC possible for their project. They almost all claim cheapest is the motivation but in fact I'm willing to bet bragging rights is the real motivator (Guilty
)
That said, if you're really looking to keep the cost as low as possible then...
Don't use an 7 Segment display, with a little a 3 I/O pins you can display 6 LEDs (Most chargers only have a single LED anyway) with 4 I/O you can display 12 LEDs. Look on Microchips site for Tips & Tricks in the app notes section. (great reading too)
Use a PIC with enough I/O to get the job done with as little glue logic as possible. There are 100s of PIC choices, you can almost always find one that fits the bill.
One very old but application specific chip that comes to mind for battery charging apps is the PIC14000
But it's not cheap, so lets see a PIC16F716 has A/D & PWM (enhanced too) and a volume production price of $0.73 and enough I/O to run a MAN6740 display in Charlieplex mode (8 or 9 pins with dp).
Just thought of this, not tested but should work...
**broken link removed**