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	$63.68	11.493%	$70.9987	$71.00	$71.00	$71.00
Purchase #2	$102.66	6.103%	$108.9253	$108.93	$108.95	$108.90
Purchase #3	$225.61	7.194%	$241.8404	$241.84	$241.85	$241.80
Purchase #4	$158.32	4.127%	$164.8539	$164.85	$164.85	$164.90
Purchase #5	$164.51	10.490%	$181.7671	$181.77	$181.75	$181.80
Purchase #6	$55.89	11.763%	$62.4643	$62.46	$62.45	$62.50
Purchase #7	$99.65	12.563%	$112.169	$112.17	$112.15	$112.20
7 purchase totals =	$870.32		$943.0187	$943.02	$943.00	$943.10