I made a French video before new graphical instructions, so it’s a bit messy on chart, but that was a good code before that: https://www.prorealcode.com/blog/video-tutorials/trading-des-chiffres-ronds-grace-a-probuilder/

Here is the code: 

//round number to nearest upper 25
roundnumber = 50

for i = 1 to roundnumber do
if (close+i*pointsize) mod roundnumber*pointsize = 0 then
upper = round(close+i*pointsize)
if upper mod roundnumber = 1 then
upper = upper-1
endif
break
endif
next

for i = roundnumber downto 1 do
if (close-i*pointsize) mod roundnumber*pointsize = 0 then
lower = round(close-i*pointsize)
if lower mod roundnumber = 1 then
lower = lower-1
endif
break
endif
next

for i = 1 to roundnumber do
if (upper+i*pointsize) mod roundnumber*pointsize = 0 then
upper1 = round(upper+i*pointsize)
if upper1 mod roundnumber = 1 then
upper1 = upper1-1
endif
break
endif
next

for i = roundnumber downto 1 do
if (lower-i*pointsize) mod roundnumber*pointsize = 0 then
lower1 = round(lower-i*pointsize)
if lower1 mod roundnumber = 1 then
lower1 = lower1-1
endif
break
endif
next


return upper, lower, upper1, lower1

I’m sorry, very busy now so I can’t transform it now with DRAWSEGMENT or DRAWHLINE, maybe someone could help?