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	$236.55	7.602%	$254.5325	$254.53	$254.55	$254.50
Purchase #2	$127.43	12.724%	$143.6442	$143.64	$143.65	$143.60
Purchase #3	$41.38	12.637%	$46.6092	$46.61	$46.60	$46.60
Purchase #4	$166.94	10.523%	$184.5071	$184.51	$184.50	$184.50
Purchase #5	$235.92	5.340%	$248.5181	$248.52	$248.50	$248.50
Purchase #6	$45.82	5.264%	$48.232	$48.23	$48.25	$48.20
Purchase #7	$235.51	7.556%	$253.3051	$253.31	$253.30	$253.30
7 purchase totals =	$1,089.55		$1,179.3482	$1,179.35	$1,179.35	$1,179.20