If you round the result at each step, which is what happens on TurboTax's Keogh, SEP and SIMPLE Contribution Worksheet, the calculation becomes:
Round($5,000 * 0.9235) = $4,618
Round($4,618 * 0.153) = $707
Round($707 / 2) = $354
$5000 - $354 = $4,646
