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	$203.58	13.272%	$230.5991	$230.60	$230.60	$230.60
Purchase #2	$147.76	13.849%	$168.2233	$168.22	$168.20	$168.20
Purchase #3	$40.96	6.383%	$43.5745	$43.57	$43.55	$43.60
Purchase #4	$208.61	12.824%	$235.3621	$235.36	$235.35	$235.40
Purchase #5	$18.96	8.468%	$20.5655	$20.57	$20.55	$20.60
Purchase #6	$219.85	3.296%	$227.0963	$227.10	$227.10	$227.10
Purchase #7	$140.35	4.342%	$146.444	$146.44	$146.45	$146.40
7 purchase totals =	$980.07		$1,071.8648	$1,071.86	$1,071.80	$1,071.90