Strange/odd outcome in decimals

[snippsat]

It might be explainable, maybe even mathematical, but I still can't figure out why this happens. Someone has an idea?

Basic answer about Floating-Point arithmetic.
Floating Point Arithmetic: Issues and Limitations

In most cases it doesn't matter as it close enough,
there is decimal that can help eg if doing financial calculation where this can matter.

from decimal import Decimal

pennies = input('Enter pennies: ')
dollars = Decimal(pennies) * Decimal('.01')
print(f'{pennies} pennies are worth ${dollars} in dollars')

Output:
Enter pennies: 35
35 pennies are worth $0.35 in dollars

from decimal import Decimal

for item in range(10):
    print(Decimal(item) * Decimal('0.4'))

Output:
0.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
3.6