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	$176.38	12.326%	$198.1206	$198.12	$198.10	$198.10
Purchase #2	$250.74	11.704%	$280.0866	$280.09	$280.10	$280.10
Purchase #3	$19.42	5.356%	$20.4601	$20.46	$20.45	$20.50
Purchase #4	$225.55	13.167%	$255.2482	$255.25	$255.25	$255.20
Purchase #5	$78.58	13.357%	$89.0759	$89.08	$89.10	$89.10
Purchase #6	$173.60	11.640%	$193.807	$193.81	$193.80	$193.80
Purchase #7	$108.75	13.107%	$123.0039	$123.00	$123.00	$123.00
7 purchase totals =	$1,033.02		$1,159.8023	$1,159.81	$1,159.80	$1,159.80