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	$10.25	10.242%	$11.2998	$11.30	$11.30	$11.30
Purchase #2	$76.28	13.599%	$86.6533	$86.65	$86.65	$86.70
Purchase #3	$169.89	13.205%	$192.324	$192.32	$192.30	$192.30
Purchase #4	$31.31	9.302%	$34.2225	$34.22	$34.20	$34.20
Purchase #5	$178.75	10.130%	$196.8574	$196.86	$196.85	$196.90
Purchase #6	$24.87	10.522%	$27.4868	$27.49	$27.50	$27.50
Purchase #7	$112.87	11.290%	$125.613	$125.61	$125.60	$125.60
7 purchase totals =	$604.22		$674.4568	$674.45	$674.40	$674.50