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	$198.85	12.244%	$223.1972	$223.20	$223.20	$223.20
Purchase #2	$137.46	5.664%	$145.2457	$145.25	$145.25	$145.20
Purchase #3	$101.29	10.231%	$111.653	$111.65	$111.65	$111.70
Purchase #4	$219.60	3.413%	$227.0949	$227.09	$227.10	$227.10
Purchase #5	$249.64	9.769%	$274.0273	$274.03	$274.05	$274.00
Purchase #6	$141.32	4.342%	$147.4561	$147.46	$147.45	$147.50
Purchase #7	$130.77	11.524%	$145.8399	$145.84	$145.85	$145.80
7 purchase totals =	$1,178.93		$1,274.5141	$1,274.52	$1,274.55	$1,274.50