Fix Banker's rounding type check test failure

[GregoryTravis]

Change was introduced by the recent re-implementation using a builtin.

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• The documentation has been updated, if necessary.
• Screenshots/screencasts have been attached, if there are any visual changes. For interactive or animated visual changes, a screencast is preferred.
• All code follows the
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  and
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  style guides. In case you are using a language not listed above, follow the Rust style guide.
• Unit tests have been written where possible.