REPORT zwvtest.
PARAMETERS: p_in TYPE dec11_4,
p_out TYPE dec11_4.
DATA: l_fraction TYPE dec11_4,
l_upper TYPE dec11_4,
l_delta_upper TYPE dec11_4,
l_lower TYPE dec11_4,
l_delta_lower TYPE dec11_4.
AT SELECTION-SCREEN.
l_fraction = FRAC( p_in * 10 ) / 10.
l_upper = CEIL( l_fraction * 20 ) / 20.
l_delta_upper = l_upper - l_fraction.
l_lower = FLOOR( l_fraction * 20 ) / 20.
l_delta_lower = l_fraction - l_lower.
IF l_delta_lower < l_delta_upper.
p_out = p_in - l_delta_lower.
ELSE.
p_out = p_in + l_delta_upper.
ENDIF.
...if you want it rounded up or down depending on what's the closest value.