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	$104.78	6.525%	$111.6169	$111.62	$111.60	$111.60
Purchase #2	$162.49	10.174%	$179.0217	$179.02	$179.00	$179.00
Purchase #3	$25.90	4.233%	$26.9963	$27.00	$27.00	$27.00
Purchase #4	$12.32	6.651%	$13.1394	$13.14	$13.15	$13.10
Purchase #5	$80.77	4.862%	$84.697	$84.70	$84.70	$84.70
Purchase #6	$226.72	3.139%	$233.8367	$233.84	$233.85	$233.80
Purchase #7	$54.80	11.571%	$61.1409	$61.14	$61.15	$61.10
7 purchase totals =	$667.78		$710.4489	$710.46	$710.45	$710.30