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	$109.28	8.493%	$118.5612	$118.56	$118.55	$118.60
Purchase #2	$156.74	11.690%	$175.0629	$175.06	$175.05	$175.10
Purchase #3	$12.59	5.853%	$13.3269	$13.33	$13.35	$13.30
Purchase #4	$239.37	3.389%	$247.4822	$247.48	$247.50	$247.50
Purchase #5	$29.88	11.162%	$33.2152	$33.22	$33.20	$33.20
Purchase #6	$187.52	4.676%	$196.2884	$196.29	$196.30	$196.30
Purchase #7	$226.44	11.558%	$252.6119	$252.61	$252.60	$252.60
7 purchase totals =	$961.82		$1,036.5487	$1,036.55	$1,036.55	$1,036.60