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	$184.48	11.336%	$205.3927	$205.39	$205.40	$205.40
Purchase #2	$70.42	4.488%	$73.5804	$73.58	$73.60	$73.60
Purchase #3	$85.84	4.791%	$89.9526	$89.95	$89.95	$90.00
Purchase #4	$11.54	7.857%	$12.4467	$12.45	$12.45	$12.40
Purchase #5	$224.98	13.728%	$255.8653	$255.87	$255.85	$255.90
Purchase #6	$102.87	8.140%	$111.2436	$111.24	$111.25	$111.20
Purchase #7	$81.65	3.608%	$84.5959	$84.60	$84.60	$84.60
7 purchase totals =	$761.78		$833.0772	$833.08	$833.10	$833.10