If you calculate the number of characters you'll be printing, you can use the cout.width() member. The cout.width() member function will automatically fill the blank area with whitespace to right align the next output with the width you specify. You can change the fill character with cout.fill(), I believe.
// Just assign the character arrays for now
// for simplicity.
char chInt[] = "Interest Rate:";
char chIntRate[] = "4.56%";
char chPrinc[] = "Principle:";
char chPrinciple[] = "$9 876.54";
// bring into namespace
using std::cout;
using std::endl;
// print out the formatted results
cout << chInt;
cout.width(40 - sizeof(chInt));
cout << chIntRate << endl;
cout << chPrinc;
cout.width(40 - sizeof(chPrinc));
cout << chPrinciple << endl;
return 0;