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	$156.95	9.745%	$172.2448	$172.24	$172.25	$172.20
Purchase #2	$20.44	4.161%	$21.2905	$21.29	$21.30	$21.30
Purchase #3	$127.91	9.181%	$139.6534	$139.65	$139.65	$139.70
Purchase #4	$150.49	13.223%	$170.3893	$170.39	$170.40	$170.40
Purchase #5	$90.91	13.249%	$102.9547	$102.95	$102.95	$103.00
Purchase #6	$216.30	5.162%	$227.4654	$227.47	$227.45	$227.50
Purchase #7	$177.82	3.643%	$184.298	$184.30	$184.30	$184.30
7 purchase totals =	$940.82		$1,018.2961	$1,018.29	$1,018.30	$1,018.40