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	$190.46	9.675%	$208.887	$208.89	$208.90	$208.90
Purchase #2	$30.94	11.367%	$34.4569	$34.46	$34.45	$34.50
Purchase #3	$144.70	7.631%	$155.7421	$155.74	$155.75	$155.70
Purchase #4	$244.49	7.469%	$262.751	$262.75	$262.75	$262.80
Purchase #5	$144.49	11.330%	$160.8607	$160.86	$160.85	$160.90
Purchase #6	$124.32	10.210%	$137.0131	$137.01	$137.00	$137.00
Purchase #7	$127.59	10.635%	$141.1592	$141.16	$141.15	$141.20
7 purchase totals =	$1,006.99		$1,100.8700	$1,100.87	$1,100.85	$1,101.00