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	$112.84	9.434%	$123.4853	$123.49	$123.50	$123.50
Purchase #2	$188.64	13.817%	$214.7044	$214.70	$214.70	$214.70
Purchase #3	$214.58	5.139%	$225.6073	$225.61	$225.60	$225.60
Purchase #4	$104.40	7.333%	$112.0557	$112.06	$112.05	$112.10
Purchase #5	$217.83	9.362%	$238.2232	$238.22	$238.20	$238.20
Purchase #6	$105.42	7.763%	$113.6038	$113.60	$113.60	$113.60
Purchase #7	$45.64	6.700%	$48.6979	$48.70	$48.70	$48.70
7 purchase totals =	$989.35		$1,076.3776	$1,076.38	$1,076.35	$1,076.40