No, 10.5 font is not too small for a resume. In fact, depending on the type of font you use, even size 10 can be okay as long as your resume is still easy to read.
Be aware that some fonts look smaller than others. If you want to use any of the following fonts on your resume, use a font size bigger than 10 points:
- Garamond
- Gill Sans
- Futura
- Bodoni
- Italic fonts