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	$112.71	12.449%	$126.7413	$126.74	$126.75	$126.70
Purchase #2	$179.65	6.294%	$190.9572	$190.96	$190.95	$191.00
Purchase #3	$58.94	13.485%	$66.8881	$66.89	$66.90	$66.90
Purchase #4	$114.51	11.675%	$127.879	$127.88	$127.90	$127.90
Purchase #5	$123.99	5.195%	$130.4313	$130.43	$130.45	$130.40
Purchase #6	$35.61	8.246%	$38.5464	$38.55	$38.55	$38.50
Purchase #7	$5.74	11.853%	$6.4204	$6.42	$6.40	$6.40
7 purchase totals =	$631.15		$687.8637	$687.87	$687.90	$687.80