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	$50.29	11.495%	$56.0708	$56.07	$56.05	$56.10
Purchase #2	$168.58	5.635%	$178.0795	$178.08	$178.10	$178.10
Purchase #3	$163.59	13.817%	$186.1932	$186.19	$186.20	$186.20
Purchase #4	$64.57	4.184%	$67.2716	$67.27	$67.25	$67.30
Purchase #5	$250.35	13.622%	$284.4527	$284.45	$284.45	$284.50
Purchase #6	$59.47	4.244%	$61.9939	$61.99	$62.00	$62.00
Purchase #7	$207.78	7.111%	$222.5552	$222.56	$222.55	$222.60
7 purchase totals =	$964.63		$1,056.6169	$1,056.61	$1,056.60	$1,056.80