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	$222.45	6.153%	$236.1373	$236.14	$236.15	$236.10
Purchase #2	$92.52	9.468%	$101.2798	$101.28	$101.30	$101.30
Purchase #3	$230.88	4.748%	$241.8422	$241.84	$241.85	$241.80
Purchase #4	$187.54	5.781%	$198.3817	$198.38	$198.40	$198.40
Purchase #5	$100.56	11.189%	$111.8117	$111.81	$111.80	$111.80
Purchase #6	$105.51	6.544%	$112.4146	$112.41	$112.40	$112.40
Purchase #7	$202.38	7.409%	$217.3743	$217.37	$217.35	$217.40
7 purchase totals =	$1,141.84		$1,219.2416	$1,219.23	$1,219.25	$1,219.20