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	$144.57	6.579%	$154.0813	$154.08	$154.10	$154.10
Purchase #2	$157.29	5.773%	$166.3704	$166.37	$166.35	$166.40
Purchase #3	$155.95	9.565%	$170.8666	$170.87	$170.85	$170.90
Purchase #4	$51.47	3.615%	$53.3306	$53.33	$53.35	$53.30
Purchase #5	$32.72	10.229%	$36.0669	$36.07	$36.05	$36.10
Purchase #6	$152.63	12.739%	$172.0735	$172.07	$172.05	$172.10
Purchase #7	$92.82	8.379%	$100.5974	$100.60	$100.60	$100.60
7 purchase totals =	$787.45		$853.3867	$853.39	$853.35	$853.50