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	$106.48	4.504%	$111.2759	$111.28	$111.30	$111.30
Purchase #2	$24.27	6.402%	$25.8238	$25.82	$25.80	$25.80
Purchase #3	$121.40	5.192%	$127.7031	$127.70	$127.70	$127.70
Purchase #4	$68.92	3.776%	$71.5224	$71.52	$71.50	$71.50
Purchase #5	$15.67	5.602%	$16.5478	$16.55	$16.55	$16.50
Purchase #6	$117.96	7.335%	$126.6124	$126.61	$126.60	$126.60
Purchase #7	$68.71	13.265%	$77.8244	$77.82	$77.80	$77.80
7 purchase totals =	$523.41		$557.3098	$557.30	$557.25	$557.20