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	$62.59	10.349%	$69.0674	$69.07	$69.05	$69.10
Purchase #2	$185.75	12.221%	$208.4505	$208.45	$208.45	$208.50
Purchase #3	$210.67	13.320%	$238.7312	$238.73	$238.75	$238.70
Purchase #4	$151.65	4.349%	$158.2453	$158.25	$158.25	$158.20
Purchase #5	$151.89	10.569%	$167.9433	$167.94	$167.95	$167.90
Purchase #6	$23.87	7.500%	$25.6603	$25.66	$25.65	$25.70
Purchase #7	$133.64	13.357%	$151.4903	$151.49	$151.50	$151.50
7 purchase totals =	$920.06		$1,019.5883	$1,019.59	$1,019.60	$1,019.60