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	$150.29	11.324%	$167.3088	$167.31	$167.30	$167.30
Purchase #2	$60.47	5.212%	$63.6217	$63.62	$63.60	$63.60
Purchase #3	$247.77	13.152%	$280.3567	$280.36	$280.35	$280.40
Purchase #4	$206.67	7.324%	$221.8065	$221.81	$221.80	$221.80
Purchase #5	$148.51	12.752%	$167.448	$167.45	$167.45	$167.40
Purchase #6	$125.94	5.721%	$133.145	$133.15	$133.15	$133.10
Purchase #7	$51.51	4.721%	$53.9418	$53.94	$53.95	$53.90
7 purchase totals =	$991.16		$1,087.6285	$1,087.64	$1,087.60	$1,087.50