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	$39.35	9.513%	$43.0934	$43.09	$43.10	$43.10
Purchase #2	$202.80	12.351%	$227.8478	$227.85	$227.85	$227.80
Purchase #3	$230.87	6.232%	$245.2578	$245.26	$245.25	$245.30
Purchase #4	$105.88	5.125%	$111.3064	$111.31	$111.30	$111.30
Purchase #5	$145.85	12.640%	$164.2854	$164.29	$164.30	$164.30
Purchase #6	$146.80	4.854%	$153.9257	$153.93	$153.95	$153.90
Purchase #7	$175.68	10.294%	$193.7645	$193.76	$193.75	$193.80
7 purchase totals =	$1,047.23		$1,139.4810	$1,139.49	$1,139.50	$1,139.50