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	$123.36	5.826%	$130.547	$130.55	$130.55	$130.50
Purchase #2	$166.60	5.402%	$175.5997	$175.60	$175.60	$175.60
Purchase #3	$164.75	8.168%	$178.2068	$178.21	$178.20	$178.20
Purchase #4	$133.78	11.730%	$149.4724	$149.47	$149.45	$149.50
Purchase #5	$162.81	6.636%	$173.6141	$173.61	$173.60	$173.60
Purchase #6	$71.39	13.390%	$80.9491	$80.95	$80.95	$80.90
Purchase #7	$246.51	13.652%	$280.1635	$280.16	$280.15	$280.20
7 purchase totals =	$1,069.20		$1,168.5526	$1,168.55	$1,168.50	$1,168.50