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	$228.39	5.544%	$241.0519	$241.05	$241.05	$241.10
Purchase #2	$108.64	6.833%	$116.0634	$116.06	$116.05	$116.10
Purchase #3	$226.53	13.352%	$256.7763	$256.78	$256.80	$256.80
Purchase #4	$13.84	12.122%	$15.5177	$15.52	$15.50	$15.50
Purchase #5	$109.45	3.384%	$113.1538	$113.15	$113.15	$113.20
Purchase #6	$78.45	6.678%	$83.6889	$83.69	$83.70	$83.70
Purchase #7	$101.38	10.320%	$111.8424	$111.84	$111.85	$111.80
7 purchase totals =	$866.68		$938.0944	$938.09	$938.10	$938.20