Hello jimlef,

Do you mean this?

	RLOG(Format(
		"Pi(2): %.02f\n"
		"PI(4): %.04f\n"
		"PI(8): %.08f\n",
		roundr(M_PI, 2),
		roundr(M_PI, 4),
		roundr(M_PI, 8)
		));

	double tax = 0.0800000000123;
	String stax = FormatG(tax, 3);
	RLOG("Formatted tax: " << stax);
	RLOG("Scanned   tax: " << ScanDouble(stax));

	Json jtax_r("tax-rounded", roundr(tax, 2));
	Json jtax_n("tax", tax);

	RDUMP(jtax_r);
	RDUMP(jtax_n);

Pi(2): 3.10
PI(4): 3.1420
PI(8): 3.14159270

Formatted tax: 0.08
Scanned   tax: 0.08
jtax_r = {"tax-rounded":0.08}
jtax_n = {"tax":0.0800000000123}

[Edit: Code updated.]

Best regards,
Oblivion