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	$182.59	5.452%	$192.5448	$192.54	$192.55	$192.50
Purchase #2	$73.41	6.375%	$78.0899	$78.09	$78.10	$78.10
Purchase #3	$120.60	5.354%	$127.0569	$127.06	$127.05	$127.10
Purchase #4	$186.65	12.424%	$209.8394	$209.84	$209.85	$209.80
Purchase #5	$169.75	13.239%	$192.2232	$192.22	$192.20	$192.20
Purchase #6	$107.43	3.804%	$111.5166	$111.52	$111.50	$111.50
Purchase #7	$79.38	10.362%	$87.6054	$87.61	$87.60	$87.60
7 purchase totals =	$919.81		$998.8762	$998.88	$998.85	$998.80