After a while in any retail point of sale system, you are going to get on your print smudges and lines appearing. Also, the number of paper jams will start to increase. If allowed to continue the printer will become unusable. Cleaning your printer is required.
Here are some steps.
What you will need
I recommend you make a solution of white vinegar and water rather than any of the prepared cleaning solutions.
Some cloth, e.g. a cleaning cloth or an old cotton rag
If you have a small vacuum cleaner which you can get in most electrical shops.
Some small brushes again which you can get in most electrical shops.
Some mechanical attribute
Please do not use compressed air; if you do not know what you are doing what you might end out doing is blowing the dust and moisture into places it should not go. It is just adding problems.
Steps to do:-
Turn off the printer, take all wires off it before attempting to clean
Wait a while some five (5) minutes before starting to clean.
Dim the lights, as in some printers the internals do not like bright light.
Now throughout the clean, avoid any electrical items and all electronics. Only there use a dry cloth. Do not touch anything electrical. You can damage it.
Remove and open what you can, eg the toner cartridge and clean those items.
Look for dirt and gently lift it. The brushes and vacuum cleaners can help here a lot.
Where there is nothing electrical use the moist cotton cloth, make sure that it is not wet.
The spilled toner, dust, hair, and built-up old paper fragments can gum up your printer and sometimes will need some real elbow grease to remove.
Do not worry if you have only done say 70%. It should be enough. Better too little than too much.
Now put it back together again.
Now clean the outside, with a moist cloth, I find for hard to remove stains AJAX very good.
However, make sure that nothing is wet.
Now dry the outside.
Wait a few minutes to let any residual water dry off and only then turn on the printer.
A clean printer beside being less of an eyesore in the shop, will print better and also last longer.
I hope this helps.