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	$116.27	8.741%	$126.4332	$126.43	$126.45	$126.40
Purchase #2	$39.88	13.592%	$45.3005	$45.30	$45.30	$45.30
Purchase #3	$196.49	13.477%	$222.971	$222.97	$222.95	$223.00
Purchase #4	$225.42	3.704%	$233.7696	$233.77	$233.75	$233.80
Purchase #5	$136.92	4.838%	$143.5442	$143.54	$143.55	$143.50
Purchase #6	$191.49	7.534%	$205.9169	$205.92	$205.90	$205.90
Purchase #7	$105.34	12.138%	$118.1262	$118.13	$118.15	$118.10
7 purchase totals =	$1,011.81		$1,096.0616	$1,096.06	$1,096.05	$1,096.00