<pre>
The answer is 77:

 a) 5c  = 1 or 5;
 b) 10c = 1 or 2 a's (1,2,6,10)
 c) 25c = 1 or 2 b's + 1 a
 d) 50c = 1 or 2 c's
 e) $1  = 1 or 2 d's

 total	penny	nickel	dime	quarter	half
 5		1	2	1	1
 6		3	1	1	1
 7		5		1	1
 8		4	3		1
 9		6	2		1
 10		8	1		1
 11		10			1
 12		7	4	1
 13		9	3	1
 14		11	2	1
 15		13	1	1
 16		15		1
 17		14	3
 18		16	2
 19		18	1
 20		20
 21	5	13	3
 22	5	15	2
 23	5	17	1
 24	5	19
 25	10	12	3
 26	10	14	2
 27	10	16	1
 28	10	18
 29	15	11	3
 30	15	13	2
 31	15	15	1
 32	15	17
 33	20	10	3
 34	20	12	2
 35	20	14	1
 36	20	16
 37	25	9	3
 38	25	11	2
 39	25	13	1
 40	25	15
 41	30	8	3
 42	30	10	2
 43	30	12	1
 44	30	14
 45	35	7	3
 46	35	9	2
 47	35	11	1
 48	35	13
 49	40	6	3
 50	40	8	2
 51	40	10	1
 52	40	12
 53	45	5	3
 54	45	7	2
 55	45	9	1
 56	45	11
 57	50	4	3
 58	50	6	2
 59	50	8	1
 60	50	10
 61	55	3	3
 62	55	5	2
 63	55	7	1
 64	55	9
 65	60	2	3
 66	60	4	2
 67	60	6	1
 68	60	8
 69	65	1	3
 70	65	3	2
 71	65	5	1
 72	65	7
 73	70		3
 74	70	2	2
 75	70	4	1
 76	70	6
 77	can't be done
 78	75	1	2
 79	75	3	1
 80	75	5
 81	can't be done
 82	80		2
 83	80	2	1
 84	80	4
 85	can't be done
 86	can't be done
 87	85	1	1
 88	85	3
 89	can't be done
 90	can't be done
 91	90		1
 92	90	2
 93-95	can't be done
 96	95	1
 97-99	can't be done
 100	100
</pre>
