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	$151.60	4.509%	$158.4356	$158.44	$158.45	$158.40
Purchase #2	$190.98	5.807%	$202.0702	$202.07	$202.05	$202.10
Purchase #3	$167.79	6.470%	$178.646	$178.65	$178.65	$178.60
Purchase #4	$135.37	6.642%	$144.3613	$144.36	$144.35	$144.40
Purchase #5	$21.76	12.118%	$24.3969	$24.40	$24.40	$24.40
Purchase #6	$92.51	11.810%	$103.4354	$103.44	$103.45	$103.40
Purchase #7	$241.55	5.631%	$255.1517	$255.15	$255.15	$255.20
7 purchase totals =	$1,001.56		$1,066.4971	$1,066.51	$1,066.50	$1,066.50