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	$200.86	9.482%	$219.9055	$219.91	$219.90	$219.90
Purchase #2	$14.90	4.570%	$15.5809	$15.58	$15.60	$15.60
Purchase #3	$173.59	6.788%	$185.3733	$185.37	$185.35	$185.40
Purchase #4	$36.71	10.299%	$40.4908	$40.49	$40.50	$40.50
Purchase #5	$71.82	12.211%	$80.5899	$80.59	$80.60	$80.60
Purchase #6	$70.39	10.313%	$77.6493	$77.65	$77.65	$77.60
Purchase #7	$177.52	3.666%	$184.0279	$184.03	$184.05	$184.00
7 purchase totals =	$745.79		$803.6176	$803.62	$803.65	$803.60