I assume you are talking in terms of rounding, in which case subtract/add half the value to which the number is rounded to get the lower and upper bounds, and then the lower bound is inclusive and the upper bound is exclusive:
- To the nearest whole number: 999.5 ≤ x < 1000.5
- To the nearest 2: 999 ≤ x < 1001
- To the nearest 4: 998 ≤ x < 1002
- To the nearest 5: 997.5 ≤ x < 1002.5
- To the nearest 8: 996 ≤ x < 1004
- To the nearest 10: 995 ≤ x < 1005
- To the nearest 20: 990 ≤ x < 1010
- To the nearest 25: 987.5 ≤ x < 1012.5
- To the nearest 40: 980 ≤ x < 1020
- To the nearest 50: 975 ≤ x < 1025
- To the nearest 100: 950 ≤ x < 1050
- To the nearest 125: 937.5 ≤ x < 1067.5
- To the nearest 200: 900 ≤ x < 1100
- To the nearest 250: 875 ≤ x < 1125
- To the nearest 500: 750 ≤ x < 1250
- To the nearest 1000: 500 ≤ x < 1500
