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	$43.73	12.182%	$49.0572	$49.06	$49.05	$49.10
Purchase #2	$114.71	11.537%	$127.9441	$127.94	$127.95	$127.90
Purchase #3	$204.72	3.316%	$211.5085	$211.51	$211.50	$211.50
Purchase #4	$183.45	6.548%	$195.4623	$195.46	$195.45	$195.50
Purchase #5	$115.35	7.519%	$124.0232	$124.02	$124.00	$124.00
Purchase #6	$150.81	5.724%	$159.4424	$159.44	$159.45	$159.40
Purchase #7	$205.73	5.699%	$217.4546	$217.45	$217.45	$217.50
7 purchase totals =	$1,018.50		$1,084.8923	$1,084.88	$1,084.85	$1,084.90