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	$200.76	3.357%	$207.4995	$207.50	$207.50	$207.50
Purchase #2	$19.32	13.550%	$21.9379	$21.94	$21.95	$21.90
Purchase #3	$229.41	12.625%	$258.373	$258.37	$258.35	$258.40
Purchase #4	$142.37	11.386%	$158.5802	$158.58	$158.60	$158.60
Purchase #5	$115.31	9.472%	$126.2322	$126.23	$126.25	$126.20
Purchase #6	$9.43	12.249%	$10.5851	$10.59	$10.60	$10.60
Purchase #7	$114.41	11.255%	$127.2868	$127.29	$127.30	$127.30
7 purchase totals =	$831.01		$910.4947	$910.50	$910.55	$910.50