$4.00 - $3.34 = $0.66 = 66 c

the coins can be 1c, 5c, 10c, 25c, 50c

let

a = the number of 1c coins, a>=0, a<=66

b = the number of 5c coins, b>=0, b <=13 (since 5b <=66)

c = the number of 10c coins, c>=0, c<=6 (since 10c <= 66)

d = the number of 25c coins, d>=0, d <=2 (since 25d <= 66)

e = the number of 50c coins, e>=0, e <=1 (since 50e <= 66)

a, b, c, d and e are integers

a + 5b + 10c + 25d + 50e = 66

start giving values to a,b,c,d and with respect to the inequalities and you will be able to write down all the combinations.