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	$132.46	10.746%	$146.6942	$146.69	$146.70	$146.70
Purchase #2	$21.31	12.410%	$23.9546	$23.95	$23.95	$24.00
Purchase #3	$105.47	6.671%	$112.5059	$112.51	$112.50	$112.50
Purchase #4	$122.90	12.535%	$138.3055	$138.31	$138.30	$138.30
Purchase #5	$106.26	4.461%	$111.0003	$111.00	$111.00	$111.00
Purchase #6	$14.35	5.191%	$15.0949	$15.09	$15.10	$15.10
Purchase #7	$162.43	5.838%	$171.9127	$171.91	$171.90	$171.90
7 purchase totals =	$665.18		$719.4681	$719.46	$719.45	$719.50