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	$160.26	4.429%	$167.3579	$167.36	$167.35	$167.40
Purchase #2	$28.67	13.346%	$32.4963	$32.50	$32.50	$32.50
Purchase #3	$204.30	11.456%	$227.7046	$227.70	$227.70	$227.70
Purchase #4	$233.50	3.542%	$241.7706	$241.77	$241.75	$241.80
Purchase #5	$181.39	13.251%	$205.426	$205.43	$205.45	$205.40
Purchase #6	$116.69	10.111%	$128.4885	$128.49	$128.50	$128.50
Purchase #7	$72.75	4.849%	$76.2776	$76.28	$76.30	$76.30
7 purchase totals =	$997.56		$1,079.5215	$1,079.53	$1,079.55	$1,079.60