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	$153.57	10.629%	$169.893	$169.89	$169.90	$169.90
Purchase #2	$224.61	6.677%	$239.6072	$239.61	$239.60	$239.60
Purchase #3	$247.38	11.284%	$275.2944	$275.29	$275.30	$275.30
Purchase #4	$80.49	12.430%	$90.4949	$90.49	$90.50	$90.50
Purchase #5	$31.88	8.494%	$34.5879	$34.59	$34.60	$34.60
Purchase #6	$125.90	10.269%	$138.8287	$138.83	$138.85	$138.80
Purchase #7	$178.60	5.195%	$187.8783	$187.88	$187.90	$187.90
7 purchase totals =	$1,042.43		$1,136.5844	$1,136.58	$1,136.65	$1,136.60