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	$24.70	7.473%	$26.5458	$26.55	$26.55	$26.50
Purchase #2	$59.28	12.509%	$66.6953	$66.70	$66.70	$66.70
Purchase #3	$67.80	6.798%	$72.409	$72.41	$72.40	$72.40
Purchase #4	$153.39	5.293%	$161.5089	$161.51	$161.50	$161.50
Purchase #5	$158.89	4.168%	$165.5125	$165.51	$165.50	$165.50
Purchase #6	$31.53	5.518%	$33.2698	$33.27	$33.25	$33.30
Purchase #7	$64.39	3.413%	$66.5876	$66.59	$66.60	$66.60
7 purchase totals =	$559.98		$592.5289	$592.54	$592.50	$592.50