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	$213.45	11.617%	$238.2465	$238.25	$238.25	$238.20
Purchase #2	$99.53	6.253%	$105.7536	$105.75	$105.75	$105.80
Purchase #3	$12.72	4.852%	$13.3372	$13.34	$13.35	$13.30
Purchase #4	$203.31	7.827%	$219.2231	$219.22	$219.20	$219.20
Purchase #5	$201.68	6.408%	$214.6037	$214.60	$214.60	$214.60
Purchase #6	$46.90	3.509%	$48.5457	$48.55	$48.55	$48.50
Purchase #7	$52.76	13.324%	$59.7897	$59.79	$59.80	$59.80
7 purchase totals =	$830.35		$899.4995	$899.50	$899.50	$899.40