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	$123.26	7.784%	$132.8546	$132.85	$132.85	$132.90
Purchase #2	$229.80	3.670%	$238.2337	$238.23	$238.25	$238.20
Purchase #3	$133.84	12.128%	$150.0721	$150.07	$150.05	$150.10
Purchase #4	$123.35	7.791%	$132.9602	$132.96	$132.95	$133.00
Purchase #5	$184.74	7.276%	$198.1817	$198.18	$198.20	$198.20
Purchase #6	$127.60	5.500%	$134.618	$134.62	$134.60	$134.60
Purchase #7	$101.77	9.218%	$111.1512	$111.15	$111.15	$111.20
7 purchase totals =	$1,024.36		$1,098.0715	$1,098.06	$1,098.05	$1,098.20