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	$214.86	6.724%	$229.3072	$229.31	$229.30	$229.30
Purchase #2	$211.40	10.720%	$234.0621	$234.06	$234.05	$234.10
Purchase #3	$207.94	3.146%	$214.4818	$214.48	$214.50	$214.50
Purchase #4	$145.38	4.177%	$151.4525	$151.45	$151.45	$151.50
Purchase #5	$240.81	12.762%	$271.5422	$271.54	$271.55	$271.50
Purchase #6	$65.47	11.368%	$72.9126	$72.91	$72.90	$72.90
Purchase #7	$219.92	12.839%	$248.1555	$248.16	$248.15	$248.20
7 purchase totals =	$1,305.78		$1,421.9139	$1,421.91	$1,421.90	$1,422.00