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	$68.51	8.630%	$74.4224	$74.42	$74.40	$74.40
Purchase #2	$185.65	5.680%	$196.1949	$196.19	$196.20	$196.20
Purchase #3	$214.97	12.286%	$241.3812	$241.38	$241.40	$241.40
Purchase #4	$173.95	10.644%	$192.4652	$192.47	$192.45	$192.50
Purchase #5	$67.41	6.612%	$71.8671	$71.87	$71.85	$71.90
Purchase #6	$248.76	5.329%	$262.0164	$262.02	$262.00	$262.00
Purchase #7	$99.88	3.498%	$103.3738	$103.37	$103.35	$103.40
7 purchase totals =	$1,059.13		$1,141.7210	$1,141.72	$1,141.65	$1,141.80