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	$167.51	11.320%	$186.4721	$186.47	$186.45	$186.50
Purchase #2	$92.74	6.462%	$98.7329	$98.73	$98.75	$98.70
Purchase #3	$70.86	11.403%	$78.9402	$78.94	$78.95	$78.90
Purchase #4	$237.68	3.501%	$246.0012	$246.00	$246.00	$246.00
Purchase #5	$212.43	5.396%	$223.8927	$223.89	$223.90	$223.90
Purchase #6	$213.97	3.793%	$222.0859	$222.09	$222.10	$222.10
Purchase #7	$73.81	9.526%	$80.8411	$80.84	$80.85	$80.80
7 purchase totals =	$1,069.00		$1,136.9661	$1,136.96	$1,137.00	$1,136.90