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	$154.59	13.768%	$175.874	$175.87	$175.85	$175.90
Purchase #2	$53.60	11.532%	$59.7812	$59.78	$59.80	$59.80
Purchase #3	$241.68	9.175%	$263.8541	$263.85	$263.85	$263.90
Purchase #4	$113.67	12.544%	$127.9288	$127.93	$127.95	$127.90
Purchase #5	$15.78	5.721%	$16.6828	$16.68	$16.70	$16.70
Purchase #6	$108.58	5.338%	$114.376	$114.38	$114.40	$114.40
Purchase #7	$34.98	9.791%	$38.4049	$38.40	$38.40	$38.40
7 purchase totals =	$722.88		$796.9018	$796.89	$796.95	$797.00