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	$103.60	9.214%	$113.1457	$113.15	$113.15	$113.10
Purchase #2	$218.79	10.644%	$242.078	$242.08	$242.10	$242.10
Purchase #3	$115.60	3.490%	$119.6344	$119.63	$119.65	$119.60
Purchase #4	$54.49	12.244%	$61.1618	$61.16	$61.15	$61.20
Purchase #5	$190.79	4.873%	$200.0872	$200.09	$200.10	$200.10
Purchase #6	$103.29	7.787%	$111.3332	$111.33	$111.35	$111.30
Purchase #7	$192.72	11.272%	$214.4434	$214.44	$214.45	$214.40
7 purchase totals =	$979.28		$1,061.8837	$1,061.88	$1,061.95	$1,061.80