Since a computer must be involved, I would try to persuade the computer to do everything.
Devise a program (in C, RealBasic, VisualBasic, etc.), to monitor the sound card for incoming beeps.
The beeps are generated by an oscillator. The oscillator is triggered by a pulse from your photosensor.
You plug the oscillator output into the audio-In port of the computer.
(As an alternate, use a webcam microphone to pick up beeps coming from a speaker which is placed nearby.)
The same program could contain your commands to:
* display the running total
* create an ascii text file containing the day's tally
* save it as a file to disk.
A bit of ingenuity on your part will minimize the expense.
There are probably ways to use modern communication devices to do this job. A 'hacker' would have an easy time of it. I am not familiar with smart phones or USB protocols, so I don't know how to advise in this area.