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	$126.70	8.461%	$137.4201	$137.42	$137.40	$137.40
Purchase #2	$112.37	5.210%	$118.2245	$118.22	$118.20	$118.20
Purchase #3	$99.43	9.658%	$109.0329	$109.03	$109.05	$109.00
Purchase #4	$10.29	3.495%	$10.6496	$10.65	$10.65	$10.60
Purchase #5	$217.58	4.429%	$227.2166	$227.22	$227.20	$227.20
Purchase #6	$200.31	11.200%	$222.7447	$222.74	$222.75	$222.70
Purchase #7	$162.98	9.716%	$178.8151	$178.82	$178.80	$178.80
7 purchase totals =	$929.66		$1,004.1035	$1,004.10	$1,004.05	$1,003.90