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	$50.81	5.720%	$53.7163	$53.72	$53.70	$53.70
Purchase #2	$130.35	11.697%	$145.597	$145.60	$145.60	$145.60
Purchase #3	$22.58	4.579%	$23.6139	$23.61	$23.60	$23.60
Purchase #4	$47.67	4.257%	$49.6993	$49.70	$49.70	$49.70
Purchase #5	$151.89	13.806%	$172.8599	$172.86	$172.85	$172.90
Purchase #6	$62.34	4.733%	$65.2906	$65.29	$65.30	$65.30
Purchase #7	$73.64	12.587%	$82.9091	$82.91	$82.90	$82.90
7 purchase totals =	$539.28		$593.6861	$593.69	$593.65	$593.70