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	$219.89	9.627%	$241.0588	$241.06	$241.05	$241.10
Purchase #2	$46.25	13.142%	$52.3282	$52.33	$52.35	$52.30
Purchase #3	$164.72	13.195%	$186.4548	$186.45	$186.45	$186.50
Purchase #4	$143.49	5.807%	$151.8225	$151.82	$151.80	$151.80
Purchase #5	$133.43	7.575%	$143.5373	$143.54	$143.55	$143.50
Purchase #6	$9.61	12.559%	$10.8169	$10.82	$10.80	$10.80
Purchase #7	$140.59	12.854%	$158.6614	$158.66	$158.65	$158.70
7 purchase totals =	$857.98		$944.6799	$944.68	$944.65	$944.70