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	$138.97	9.126%	$151.6524	$151.65	$151.65	$151.70
Purchase #2	$145.62	13.257%	$164.9248	$164.92	$164.90	$164.90
Purchase #3	$130.80	9.854%	$143.689	$143.69	$143.70	$143.70
Purchase #4	$247.81	4.163%	$258.1263	$258.13	$258.15	$258.10
Purchase #5	$24.64	11.527%	$27.4803	$27.48	$27.50	$27.50
Purchase #6	$49.43	10.434%	$54.5875	$54.59	$54.60	$54.60
Purchase #7	$158.48	8.205%	$171.4833	$171.48	$171.50	$171.50
7 purchase totals =	$895.75		$971.9436	$971.94	$972.00	$972.00