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	$153.32	3.196%	$158.2201	$158.22	$158.20	$158.20
Purchase #2	$14.52	5.369%	$15.2996	$15.30	$15.30	$15.30
Purchase #3	$26.90	6.165%	$28.5584	$28.56	$28.55	$28.60
Purchase #4	$104.40	6.383%	$111.0639	$111.06	$111.05	$111.10
Purchase #5	$196.54	12.198%	$220.5139	$220.51	$220.50	$220.50
Purchase #6	$95.81	8.544%	$103.996	$104.00	$104.00	$104.00
Purchase #7	$129.33	10.564%	$142.9924	$142.99	$143.00	$143.00
7 purchase totals =	$720.82		$780.6443	$780.64	$780.60	$780.70