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	$235.60	7.757%	$253.8755	$253.88	$253.90	$253.90
Purchase #2	$138.55	3.627%	$143.5752	$143.58	$143.60	$143.60
Purchase #3	$239.41	4.208%	$249.4844	$249.48	$249.50	$249.50
Purchase #4	$95.50	8.824%	$103.9269	$103.93	$103.95	$103.90
Purchase #5	$92.58	5.232%	$97.4238	$97.42	$97.40	$97.40
Purchase #6	$112.69	9.720%	$123.6435	$123.64	$123.65	$123.60
Purchase #7	$117.77	7.831%	$126.9926	$126.99	$127.00	$127.00
7 purchase totals =	$1,032.10		$1,098.9219	$1,098.92	$1,099.00	$1,098.90