[Bug] Use toFixed

[bh2smith]

We have been getting a parse error on number types

InvalidDecimalNumberError: Number `2.22047152096e-16` is not a valid decimal number.

Version: viem@2.21.52
    details: undefined,
   docsPath: undefined,
 metaMessages: undefined,
 shortMessage: "Number `2.22047152096e-16` is not a valid decimal number.",
    version: "2.21.52",

this resolves it in the simplest, quickest way.