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	$161.85	13.591%	$183.847	$183.85	$183.85	$183.80
Purchase #2	$31.70	5.804%	$33.5399	$33.54	$33.55	$33.50
Purchase #3	$101.85	9.817%	$111.8486	$111.85	$111.85	$111.80
Purchase #4	$216.77	3.609%	$224.5932	$224.59	$224.60	$224.60
Purchase #5	$181.49	4.616%	$189.8676	$189.87	$189.85	$189.90
Purchase #6	$117.48	12.405%	$132.0534	$132.05	$132.05	$132.10
Purchase #7	$173.63	4.724%	$181.8323	$181.83	$181.85	$181.80
7 purchase totals =	$984.77		$1,057.5820	$1,057.58	$1,057.60	$1,057.50