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	$105.31	6.726%	$112.3932	$112.39	$112.40	$112.40
Purchase #2	$33.75	10.518%	$37.2998	$37.30	$37.30	$37.30
Purchase #3	$248.52	8.481%	$269.597	$269.60	$269.60	$269.60
Purchase #4	$138.94	3.568%	$143.8974	$143.90	$143.90	$143.90
Purchase #5	$178.31	10.321%	$196.7134	$196.71	$196.70	$196.70
Purchase #6	$105.38	12.405%	$118.4524	$118.45	$118.45	$118.50
Purchase #7	$159.36	13.620%	$181.0648	$181.06	$181.05	$181.10
7 purchase totals =	$969.57		$1,059.4180	$1,059.41	$1,059.40	$1,059.50