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	$198.66	12.159%	$222.8151	$222.82	$222.80	$222.80
Purchase #2	$75.51	11.774%	$84.4005	$84.40	$84.40	$84.40
Purchase #3	$132.64	11.397%	$147.757	$147.76	$147.75	$147.80
Purchase #4	$228.57	12.388%	$256.8853	$256.89	$256.90	$256.90
Purchase #5	$81.39	9.466%	$89.0944	$89.09	$89.10	$89.10
Purchase #6	$66.66	5.853%	$70.5616	$70.56	$70.55	$70.60
Purchase #7	$216.60	8.447%	$234.8962	$234.90	$234.90	$234.90
7 purchase totals =	$1,000.03		$1,106.4101	$1,106.42	$1,106.40	$1,106.50