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	$113.79	4.688%	$119.1245	$119.12	$119.10	$119.10
Purchase #2	$78.87	9.203%	$86.1284	$86.13	$86.15	$86.10
Purchase #3	$68.75	12.461%	$77.3169	$77.32	$77.30	$77.30
Purchase #4	$187.85	3.229%	$193.9157	$193.92	$193.90	$193.90
Purchase #5	$194.33	7.341%	$208.5958	$208.60	$208.60	$208.60
Purchase #6	$113.65	12.179%	$127.4914	$127.49	$127.50	$127.50
Purchase #7	$71.40	10.111%	$78.6193	$78.62	$78.60	$78.60
7 purchase totals =	$828.64		$891.1920	$891.20	$891.15	$891.10