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	$206.71	7.868%	$222.9739	$222.97	$222.95	$223.00
Purchase #2	$22.61	12.553%	$25.4482	$25.45	$25.45	$25.40
Purchase #3	$158.50	9.723%	$173.911	$173.91	$173.90	$173.90
Purchase #4	$204.83	5.579%	$216.2575	$216.26	$216.25	$216.30
Purchase #5	$148.89	13.135%	$168.4467	$168.45	$168.45	$168.40
Purchase #6	$145.91	6.366%	$155.1986	$155.20	$155.20	$155.20
Purchase #7	$114.52	11.517%	$127.7093	$127.71	$127.70	$127.70
7 purchase totals =	$1,001.97		$1,089.9452	$1,089.95	$1,089.90	$1,089.90