floating point - Rounding values less than 1 in C? -

i coding graphical program in c , cartesian values in between [-1,1], having trouble rounding off values can use them plotting , further calculations. know how round values greater 1 decimals haven't done before.

so how go rounding values? example,

.7213=.7  .7725= .8  .3666667=.4  .25=.2 or .3  .24=.2 

any suggestions gladly appreciated. :)

in languages, people implement such rounding in ad hoc way using *10, integral rounding, , /10. example:

$ cat round.c #include <stdio.h> #include <stdint.h>  int main() {     fprintf(stderr, "%f\n",     ((double)  ((uint64_t) (10*0.7777))) / 10);     return 0; }  $ gcc round.c [tommd@vodka test]$ ./a.out 0.700000