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	$176.29	8.131%	$190.6241	$190.62	$190.60	$190.60
Purchase #2	$227.68	7.351%	$244.4168	$244.42	$244.40	$244.40
Purchase #3	$229.81	11.302%	$255.7831	$255.78	$255.80	$255.80
Purchase #4	$109.27	9.728%	$119.8998	$119.90	$119.90	$119.90
Purchase #5	$15.37	3.635%	$15.9287	$15.93	$15.95	$15.90
Purchase #6	$130.89	10.263%	$144.3232	$144.32	$144.30	$144.30
Purchase #7	$235.59	11.296%	$262.2022	$262.20	$262.20	$262.20
7 purchase totals =	$1,124.90		$1,233.1779	$1,233.17	$1,233.15	$1,233.10