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	$48.51	11.509%	$54.093	$54.09	$54.10	$54.10
Purchase #2	$247.34	4.312%	$258.0053	$258.01	$258.00	$258.00
Purchase #3	$211.94	6.834%	$226.424	$226.42	$226.40	$226.40
Purchase #4	$103.75	7.375%	$111.4016	$111.40	$111.40	$111.40
Purchase #5	$37.99	11.762%	$42.4584	$42.46	$42.45	$42.50
Purchase #6	$62.35	5.536%	$65.8017	$65.80	$65.80	$65.80
Purchase #7	$200.47	7.202%	$214.9078	$214.91	$214.90	$214.90
7 purchase totals =	$912.35		$973.0918	$973.09	$973.05	$973.10