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	$159.52	13.528%	$181.0999	$181.10	$181.10	$181.10
Purchase #2	$191.95	12.717%	$216.3603	$216.36	$216.35	$216.40
Purchase #3	$146.96	3.110%	$151.5305	$151.53	$151.55	$151.50
Purchase #4	$205.58	12.182%	$230.6238	$230.62	$230.60	$230.60
Purchase #5	$157.60	5.671%	$166.5375	$166.54	$166.55	$166.50
Purchase #6	$119.82	5.109%	$125.9416	$125.94	$125.95	$125.90
Purchase #7	$84.35	7.606%	$90.7657	$90.77	$90.75	$90.80
7 purchase totals =	$1,065.78		$1,162.8593	$1,162.86	$1,162.85	$1,162.80