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	$132.44	8.606%	$143.8378	$143.84	$143.85	$143.80
Purchase #2	$13.46	9.744%	$14.7715	$14.77	$14.75	$14.80
Purchase #3	$43.69	10.852%	$48.4312	$48.43	$48.45	$48.40
Purchase #4	$216.98	7.447%	$233.1385	$233.14	$233.15	$233.10
Purchase #5	$105.34	6.119%	$111.7858	$111.79	$111.80	$111.80
Purchase #6	$178.55	11.227%	$198.5958	$198.60	$198.60	$198.60
Purchase #7	$114.39	10.851%	$126.8025	$126.80	$126.80	$126.80
7 purchase totals =	$804.85		$877.3631	$877.37	$877.40	$877.30