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	$171.25	4.361%	$178.7182	$178.72	$178.70	$178.70
Purchase #2	$160.82	12.669%	$181.1943	$181.19	$181.20	$181.20
Purchase #3	$160.35	7.840%	$172.9214	$172.92	$172.90	$172.90
Purchase #4	$40.85	9.793%	$44.8504	$44.85	$44.85	$44.90
Purchase #5	$92.91	13.311%	$105.2773	$105.28	$105.30	$105.30
Purchase #6	$64.68	13.307%	$73.287	$73.29	$73.30	$73.30
Purchase #7	$186.99	5.250%	$196.807	$196.81	$196.80	$196.80
7 purchase totals =	$877.85		$953.0556	$953.06	$953.05	$953.10