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	$233.59	13.663%	$265.5054	$265.51	$265.50	$265.50
Purchase #2	$76.36	10.149%	$84.1098	$84.11	$84.10	$84.10
Purchase #3	$83.26	4.774%	$87.2348	$87.23	$87.25	$87.20
Purchase #4	$168.28	3.174%	$173.6212	$173.62	$173.60	$173.60
Purchase #5	$37.70	12.859%	$42.5478	$42.55	$42.55	$42.50
Purchase #6	$196.53	9.126%	$214.4653	$214.47	$214.45	$214.50
Purchase #7	$203.59	13.873%	$231.834	$231.83	$231.85	$231.80
7 purchase totals =	$999.31		$1,099.3183	$1,099.32	$1,099.30	$1,099.20