You may be getting fooled by the print method of tibbles rounding the output. The full precision is still available but not displayed. Here is an example.
library(tibble)
DATA <- tibble(A = 1.234567, B =9.87654)
DATA
#> # A tibble: 1 x 2
#> A B
#> <dbl> <dbl>
#> 1 1.23 9.88
as.data.frame(DATA)
#> A B
#> 1 1.234567 9.87654
Created on 2019-05-09 by the reprex package (v0.2.1)