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	$137.25	13.623%	$155.9476	$155.95	$155.95	$155.90
Purchase #2	$39.97	13.351%	$45.3064	$45.31	$45.30	$45.30
Purchase #3	$46.28	4.299%	$48.2696	$48.27	$48.25	$48.30
Purchase #4	$219.63	8.391%	$238.0592	$238.06	$238.05	$238.10
Purchase #5	$151.80	3.342%	$156.8732	$156.87	$156.85	$156.90
Purchase #6	$23.81	7.523%	$25.6012	$25.60	$25.60	$25.60
Purchase #7	$78.38	10.824%	$86.8639	$86.86	$86.85	$86.90
7 purchase totals =	$697.12		$756.9211	$756.92	$756.85	$757.00