Based on my prior knowledge, the thousand seed weight (MHG) can have a significant impact on the grain yield of soybean cultivars. A higher thousand seed weight generally indicates larger, heavier seeds, which are likely to contribute to a higher grain yield.

To analyze the relationship between MHG and the target variable (grain yield), we can compare the values of MHG for soybean cultivars with low and high grain yield. 

Here is the generated dictionary with 5 typical values of MHG for each target class:

```json
{
	"low": [100.2, 98.5, 101.7, 99.8, 96.1],
	"high": [105.4, 104.7, 107.3, 103.6, 106.9]
}
```

Please note that these MHG values are just examples and may not represent the actual data. The values are presented as floats in the lists for better readability.