title: Slice_min and Slice_max Tie Clarification
body: <p>When does <code>dplyr</code> return ties when using <code>slice_min</code> and <code>slice_max</code>? I'm seeing some inconsistencies and can't seem to find any clarification online or in their documentation.</p>
  <p>Examples:</p>
  <pre><code>library(dplyr)
  
  #there is a tie but only returns 5 rows, not the bottom 5 mpg's
  mtcars %&gt;% slice_min(mpg, n = 5, with_ties = TRUE)
  #&gt;                      mpg cyl disp  hp drat    wt  qsec vs am gear carb
  #&gt; Cadillac Fleetwood  10.4   8  472 205 2.93 5.250 17.98  0  0    3    4
  #&gt; Lincoln Continental 10.4   8  460 215 3.00 5.424 17.82  0  0    3    4
  #&gt; Camaro Z28          13.3   8  350 245 3.73 3.840 15.41  0  0    3    4
  #&gt; Duster 360          14.3   8  360 245 3.21 3.570 15.84  0  0    3    4
  #&gt; Chrysler Imperial   14.7   8  440 230 3.23 5.345 17.42  0  0    3    4
  
  #this will return the top two as a tie when above it did not
  mtcars %&gt;%
    slice_min(mpg, n = 1, with_ties = TRUE)
  #&gt;                      mpg cyl disp  hp drat    wt  qsec vs am gear carb
  #&gt; Cadillac Fleetwood  10.4   8  472 205 2.93 5.250 17.98  0  0    3    4
  #&gt; Lincoln Continental 10.4   8  460 215 3.00 5.424 17.82  0  0    3    4
  
  #another example of it using ties to return more than 3 rows
  starwars %&gt;%
    select(gender, mass) %&gt;%
    group_by(gender) %&gt;%
    slice_min(mass, n = 3, with_ties = TRUE)
  # A tibble: 8 x 2
  # Groups:   gender [3]
  #  gender     mass
  #       
  #1 feminine     45
  #2 feminine     49
  #3 feminine     50
  #4 feminine     50
  #5 masculine    15
  #6 masculine    17
  #7 masculine    20
  #8 NA           48
  </code></pre>
  <p>Am I missing something here?</p>