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	$40.86	6.515%	$43.522	$43.52	$43.50	$43.50
Purchase #2	$62.33	6.859%	$66.6052	$66.61	$66.60	$66.60
Purchase #3	$124.80	9.847%	$137.0891	$137.09	$137.10	$137.10
Purchase #4	$52.54	3.267%	$54.2565	$54.26	$54.25	$54.30
Purchase #5	$241.32	5.312%	$254.1389	$254.14	$254.15	$254.10
Purchase #6	$244.32	9.806%	$268.278	$268.28	$268.30	$268.30
Purchase #7	$111.64	5.303%	$117.5603	$117.56	$117.55	$117.60
7 purchase totals =	$877.81		$941.4500	$941.46	$941.45	$941.50