Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$168.89	8.607%	$183.4264	$183.43	$183.45	$183.40
Purchase #2	$81.60	4.605%	$85.3577	$85.36	$85.35	$85.40
Purchase #3	$86.43	9.151%	$94.3392	$94.34	$94.35	$94.30
Purchase #4	$122.49	13.845%	$139.4487	$139.45	$139.45	$139.40
Purchase #5	$40.57	4.354%	$42.3364	$42.34	$42.35	$42.30
Purchase #6	$171.37	5.870%	$181.4294	$181.43	$181.45	$181.40
Purchase #7	$69.78	11.788%	$78.0057	$78.01	$78.00	$78.00
7 purchase totals =	$741.13		$804.3435	$804.36	$804.40	$804.20