Round numbers before statement

how can i round number on 5 decimal numbers of some result ? I have something like this...

double s;
s=d/a;s1=d1/a1;
here i need to round these 2 numbers ... because s1 is different from s by 0.00000002 etc
if(s1>s){
printf("S1 > S");
    if(s1==s){
printf("S1 = S");

someone with help with this ? Thank you