They are sort of divided into 3 tiers.

+25% it's 2 each and 10 for 5
+45% it's 10 each and 50 for 5
+65% it's 20 each and 100 for 5

Total from 0 to +65% is 160. It's much better value to +25% your whole main team then +45% rather then focus on just one ninja if you are planning to use it long term.