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	$161.81	6.745%	$172.7241	$172.72	$172.70	$172.70
Purchase #2	$194.57	11.810%	$217.5487	$217.55	$217.55	$217.50
Purchase #3	$97.82	13.792%	$111.3113	$111.31	$111.30	$111.30
Purchase #4	$48.35	13.180%	$54.7225	$54.72	$54.70	$54.70
Purchase #5	$56.69	12.871%	$63.9866	$63.99	$64.00	$64.00
Purchase #6	$165.64	3.795%	$171.926	$171.93	$171.95	$171.90
Purchase #7	$168.78	7.364%	$181.209	$181.21	$181.20	$181.20
7 purchase totals =	$893.66		$973.4282	$973.43	$973.40	$973.30