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	$103.37	7.625%	$111.252	$111.25	$111.25	$111.30
Purchase #2	$231.81	12.859%	$261.6184	$261.62	$261.60	$261.60
Purchase #3	$205.84	8.252%	$222.8259	$222.83	$222.85	$222.80
Purchase #4	$83.61	7.250%	$89.6717	$89.67	$89.65	$89.70
Purchase #5	$193.35	3.721%	$200.5446	$200.54	$200.55	$200.50
Purchase #6	$107.31	4.103%	$111.7129	$111.71	$111.70	$111.70
Purchase #7	$52.96	9.509%	$57.996	$58.00	$58.00	$58.00
7 purchase totals =	$978.25		$1,055.6215	$1,055.62	$1,055.60	$1,055.60