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	$136.25	5.389%	$143.5925	$143.59	$143.60	$143.60
Purchase #2	$7.38	3.552%	$7.6421	$7.64	$7.65	$7.60
Purchase #3	$38.34	12.871%	$43.2747	$43.27	$43.25	$43.30
Purchase #4	$214.49	12.502%	$241.3055	$241.31	$241.30	$241.30
Purchase #5	$7.99	13.615%	$9.0778	$9.08	$9.10	$9.10
Purchase #6	$229.43	12.459%	$258.0147	$258.01	$258.00	$258.00
Purchase #7	$48.91	11.681%	$54.6232	$54.62	$54.60	$54.60
7 purchase totals =	$682.79		$757.5305	$757.52	$757.50	$757.50