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	$235.37	8.605%	$255.6236	$255.62	$255.60	$255.60
Purchase #2	$68.46	4.561%	$71.5825	$71.58	$71.60	$71.60
Purchase #3	$111.46	3.539%	$115.4046	$115.40	$115.40	$115.40
Purchase #4	$164.41	5.237%	$173.0202	$173.02	$173.00	$173.00
Purchase #5	$131.66	4.513%	$137.6018	$137.60	$137.60	$137.60
Purchase #6	$40.61	7.274%	$43.564	$43.56	$43.55	$43.60
Purchase #7	$94.35	10.600%	$104.3511	$104.35	$104.35	$104.40
7 purchase totals =	$846.32		$901.1478	$901.13	$901.10	$901.20