Would be great to be able to round results to a set number of significant figures, or to a specific place value.
Examples:
• 
5 349 046 to 3 sf
→ 5 350 000
• 
2.3945 to 2 significant figures
→ 2.4
• 
3894 to nearest hundred
→ 3 900
• 
.897465 to thousandths
→ 0.897
On a related note, it might make sense to allow rounding “to x decimal place(s)” as well as the current “to x dp”.