Any number in the interval (67.95, 68.05).
68.0
0.2
100 exactly (100.00). You the tenth place is the number right next to the decimal place to the right of it. The hundredths place (next number to the right) determines whether the tenth place rounds up or down. Since it is over 5 it rounds up to 100.
9000.0499...
4592 rounds to 4592 if you round to the nearest tenth, as tenth relates to decimal figures which aren't included in the number you gave.However, 4592 rounds to 4590 if you round to the nearest ten.
When rounding to the nearest tenth (or other fraction), you always look at the next number. Here, in 15.992 the next number is 9 (second place after decimal point), therefore it rounds up. As the next number (first place after decimal point) is also 9, this also rounds up, giving the result of 16.0. (If the number to round would be for example 15.945, the result rounded to the nearest tenth would be 15.9)
15.5
0.11 rounds to:0 to the nearest whole number/unit0.1 to the nearest tenth
0.85 rounds to:1 to the nearest whole number/unit0.9 to the nearest tenth
0.18 rounds to:0 to the nearest whole number/unit0.2 to the nearest tenth
0.80 rounds to:1 to the nearest whole number/unit0.8 to the nearest tenth
8.13 rounds to:10 to the nearest ten8 to the nearest whole number/unit8.1 to the nearest tenth
20.50 rounds to20 to the nearest ten21 to the nearest whole number/unit20.5 to the nearest tenth