fix: implement rounding and remainder handling for parimutuel payouts

[popsman01]

📋 Description

Brief description of the changes in this PR.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Performance improvement
• Code refactoring

✅ Checklist

Code Quality

• Code follows project style guidelines
• Self-review completed
• Comments added for complex code
• No unnecessary console.log or debug code
• No commented-out code

Security

• Security implications considered
• No sensitive data exposed
• Input validation added
• Authorization checks in place

📊 Performance Impact

• No performance impact
• Performance improved
• Performance impact acceptable (explain below)

By submitting this PR, I confirm that:

• I have read and followed the CONTRIBUTING.md guidelines
• My code follows the project's coding standards
• I have tested my changes thoroughly
• I am ready for code review

resolves #198

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