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	$142.57	11.224%	$158.5721	$158.57	$158.55	$158.60
Purchase #2	$97.82	13.723%	$111.2438	$111.24	$111.25	$111.20
Purchase #3	$53.48	8.271%	$57.9033	$57.90	$57.90	$57.90
Purchase #4	$53.46	3.451%	$55.3049	$55.30	$55.30	$55.30
Purchase #5	$117.87	8.320%	$127.6768	$127.68	$127.70	$127.70
Purchase #6	$199.87	3.570%	$207.0054	$207.01	$207.00	$207.00
Purchase #7	$157.70	6.378%	$167.7581	$167.76	$167.75	$167.80
7 purchase totals =	$822.77		$885.4644	$885.46	$885.45	$885.50