To minimize rounding errors, perform multiplication before division. The result tends to be more accurate that way.

minimizeRoundingErrors.go

package main

import "fmt"

func main() {
	fmt.Println("1. Division First")
	celsius := 21.0
	fmt.Print((celsius/5.0*9.0)+32, "° F\n")
	fmt.Print((9.0/5.0*celsius)+32, "° F\n\n")

	fmt.Println("2. Multiplication First")
	fahrenheit := (celsius * 9.0 / 5.0) + 32.0
	fmt.Print(fahrenheit, "° F")
}

/* 
OUTPUT

1. Division First
69.80000000000001° F
69.80000000000001° F

2. Multiplication First
69.8° F

*/