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	$103.76	10.511%	$114.6662	$114.67	$114.65	$114.70
Purchase #2	$69.35	13.402%	$78.6443	$78.64	$78.65	$78.60
Purchase #3	$242.39	7.517%	$260.6105	$260.61	$260.60	$260.60
Purchase #4	$100.40	10.724%	$111.1669	$111.17	$111.15	$111.20
Purchase #5	$100.48	13.806%	$114.3523	$114.35	$114.35	$114.40
Purchase #6	$20.59	11.373%	$22.9317	$22.93	$22.95	$22.90
Purchase #7	$200.27	13.129%	$226.5634	$226.56	$226.55	$226.60
7 purchase totals =	$837.24		$928.9353	$928.93	$928.90	$929.00