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	$108.35	3.741%	$112.4034	$112.40	$112.40	$112.40
Purchase #2	$227.80	12.160%	$255.5005	$255.50	$255.50	$255.50
Purchase #3	$157.80	4.371%	$164.6974	$164.70	$164.70	$164.70
Purchase #4	$194.43	10.286%	$214.4291	$214.43	$214.45	$214.40
Purchase #5	$164.77	12.791%	$185.8457	$185.85	$185.85	$185.80
Purchase #6	$150.35	6.171%	$159.6281	$159.63	$159.65	$159.60
Purchase #7	$85.70	13.271%	$97.0732	$97.07	$97.05	$97.10
7 purchase totals =	$1,089.20		$1,189.5774	$1,189.58	$1,189.60	$1,189.50