1 – change your printer (joke), some web enabled printers (e-series of HP for exmaple) does have a dedicated e-mail address where you can send an email with an attachment to print, if your printer has this feature, just send programatically an email with that attachment to it.
2 – Use custom Java in order to print; https://docs.oracle.com/javase/tutorial/2d/printing/index.html
3 - If Windows OS, you can also print over cmd in combination with custom java ; https://superuser.com/questions/477895/printing-from-windows-7-command-line
If its a point of sale system, its probably running on custom hardware, so write a custom browser to drop all the normal end user garbage. Use Qt or the Android SDK. Friendly greetings from Centurion!