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	$99.71	11.831%	$111.5067	$111.51	$111.50	$111.50
Purchase #2	$100.26	7.320%	$107.599	$107.60	$107.60	$107.60
Purchase #3	$13.83	7.236%	$14.8307	$14.83	$14.85	$14.80
Purchase #4	$120.80	6.665%	$128.8513	$128.85	$128.85	$128.90
Purchase #5	$149.47	11.640%	$166.8683	$166.87	$166.85	$166.90
Purchase #6	$118.49	10.633%	$131.089	$131.09	$131.10	$131.10
Purchase #7	$211.66	12.720%	$238.5832	$238.58	$238.60	$238.60
7 purchase totals =	$814.22		$899.3282	$899.33	$899.35	$899.40