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	$221.71	4.169%	$230.9531	$230.95	$230.95	$231.00
Purchase #2	$64.47	10.587%	$71.2954	$71.30	$71.30	$71.30
Purchase #3	$104.71	6.131%	$111.1298	$111.13	$111.15	$111.10
Purchase #4	$170.53	3.573%	$176.623	$176.62	$176.60	$176.60
Purchase #5	$92.81	5.724%	$98.1224	$98.12	$98.10	$98.10
Purchase #6	$118.62	7.270%	$127.2437	$127.24	$127.25	$127.20
Purchase #7	$147.81	10.680%	$163.5961	$163.60	$163.60	$163.60
7 purchase totals =	$920.66		$978.9635	$978.96	$978.95	$978.90