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	$112.54	5.819%	$119.0887	$119.09	$119.10	$119.10
Purchase #2	$102.84	8.369%	$111.4467	$111.45	$111.45	$111.40
Purchase #3	$144.80	7.137%	$155.1344	$155.13	$155.15	$155.10
Purchase #4	$68.83	5.500%	$72.6157	$72.62	$72.60	$72.60
Purchase #5	$169.71	10.859%	$188.1388	$188.14	$188.15	$188.10
Purchase #6	$55.68	4.703%	$58.2986	$58.30	$58.30	$58.30
Purchase #7	$64.56	9.152%	$70.4685	$70.47	$70.45	$70.50
7 purchase totals =	$718.96		$775.1914	$775.20	$775.20	$775.10