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	$143.43	5.523%	$151.3516	$151.35	$151.35	$151.40
Purchase #2	$173.35	7.374%	$186.1328	$186.13	$186.15	$186.10
Purchase #3	$172.42	11.711%	$192.6121	$192.61	$192.60	$192.60
Purchase #4	$49.42	10.542%	$54.6299	$54.63	$54.65	$54.60
Purchase #5	$204.59	9.459%	$223.9422	$223.94	$223.95	$223.90
Purchase #6	$160.42	3.643%	$166.2641	$166.26	$166.25	$166.30
Purchase #7	$114.52	6.401%	$121.8504	$121.85	$121.85	$121.90
7 purchase totals =	$1,018.15		$1,096.7831	$1,096.77	$1,096.80	$1,096.80