This is how I'd do it. I'd declare 5 variables.
Write on them the amount of the sales.
Get the highest amount and depending on how big is it, divide it by multiples of 10 or 100.
Lets say highest sale was $1000, then you'd divide that by 100, and do the same to the others.
Also remember that the " / " operator doesnt give you the exact amount all the time, gives you a whole number.
That way you'll have a whole number for each variable related to what they sold.
The easiest way to go, is to print out the bars with symbols like "#" horizontally.
Lets say..
Andrew ########## ($1000)
Johnny ##### ($500)
Joseph ####### ($600)
.
.
and so on.
I'd suggest on using the System.out.println(""). That way you'll keep writting or adding a "#" with loop for the number given to the amount they sold.
Remeber, you can use System.out.printlm("\n") is the same as having System.out.print("") which will make you write on the next line in the command prompt.
I hope you find this helpful.