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	$232.49	10.324%	$256.4923	$256.49	$256.50	$256.50
Purchase #2	$119.81	7.828%	$129.1887	$129.19	$129.20	$129.20
Purchase #3	$156.58	10.223%	$172.5872	$172.59	$172.60	$172.60
Purchase #4	$116.79	9.237%	$127.5779	$127.58	$127.60	$127.60
Purchase #5	$231.51	10.479%	$255.7699	$255.77	$255.75	$255.80
Purchase #6	$120.47	4.726%	$126.1634	$126.16	$126.15	$126.20
Purchase #7	$22.63	13.326%	$25.6457	$25.65	$25.65	$25.60
7 purchase totals =	$1,000.28		$1,093.4251	$1,093.43	$1,093.45	$1,093.50