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	$128.94	13.629%	$146.5132	$146.51	$146.50	$146.50
Purchase #2	$248.96	9.304%	$272.1232	$272.12	$272.10	$272.10
Purchase #3	$155.84	10.110%	$171.5954	$171.60	$171.60	$171.60
Purchase #4	$100.32	11.630%	$111.9872	$111.99	$112.00	$112.00
Purchase #5	$148.31	3.455%	$153.4341	$153.43	$153.45	$153.40
Purchase #6	$114.48	11.517%	$127.6647	$127.66	$127.65	$127.70
Purchase #7	$65.27	10.146%	$71.8923	$71.89	$71.90	$71.90
7 purchase totals =	$962.12		$1,055.2101	$1,055.20	$1,055.20	$1,055.20