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	$89.32	13.124%	$101.0424	$101.04	$101.05	$101.00
Purchase #2	$71.38	10.116%	$78.6008	$78.60	$78.60	$78.60
Purchase #3	$38.65	12.429%	$43.4538	$43.45	$43.45	$43.50
Purchase #4	$152.58	3.177%	$157.4275	$157.43	$157.45	$157.40
Purchase #5	$180.61	11.510%	$201.3982	$201.40	$201.40	$201.40
Purchase #6	$99.42	11.827%	$111.1784	$111.18	$111.20	$111.20
Purchase #7	$211.61	5.245%	$222.7089	$222.71	$222.70	$222.70
7 purchase totals =	$843.57		$915.8100	$915.81	$915.85	$915.80