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	$151.48	10.133%	$166.8295	$166.83	$166.85	$166.80
Purchase #2	$149.65	9.680%	$164.1361	$164.14	$164.15	$164.10
Purchase #3	$129.50	5.484%	$136.6018	$136.60	$136.60	$136.60
Purchase #4	$52.97	6.766%	$56.554	$56.55	$56.55	$56.60
Purchase #5	$73.80	6.365%	$78.4974	$78.50	$78.50	$78.50
Purchase #6	$10.35	6.263%	$10.9982	$11.00	$11.00	$11.00
Purchase #7	$131.78	10.511%	$145.6314	$145.63	$145.65	$145.60
7 purchase totals =	$699.53		$759.2484	$759.25	$759.30	$759.20