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	$94.79	11.692%	$105.8728	$105.87	$105.85	$105.90
Purchase #2	$198.82	4.653%	$208.0711	$208.07	$208.05	$208.10
Purchase #3	$249.98	12.845%	$282.0899	$282.09	$282.10	$282.10
Purchase #4	$138.30	3.751%	$143.4876	$143.49	$143.50	$143.50
Purchase #5	$54.29	12.503%	$61.0779	$61.08	$61.10	$61.10
Purchase #6	$58.49	13.710%	$66.509	$66.51	$66.50	$66.50
Purchase #7	$240.25	10.312%	$265.0246	$265.02	$265.00	$265.00
7 purchase totals =	$1,034.92		$1,132.1329	$1,132.13	$1,132.10	$1,132.20