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	$202.68	5.659%	$214.1497	$214.15	$214.15	$214.10
Purchase #2	$231.71	3.456%	$239.7179	$239.72	$239.70	$239.70
Purchase #3	$85.84	5.660%	$90.6985	$90.70	$90.70	$90.70
Purchase #4	$151.38	6.260%	$160.8564	$160.86	$160.85	$160.90
Purchase #5	$30.49	7.755%	$32.8545	$32.85	$32.85	$32.90
Purchase #6	$127.33	4.195%	$132.6715	$132.67	$132.65	$132.70
Purchase #7	$106.76	4.527%	$111.593	$111.59	$111.60	$111.60
7 purchase totals =	$936.19		$982.5415	$982.54	$982.50	$982.60