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	$90.61	8.655%	$98.4523	$98.45	$98.45	$98.50
Purchase #2	$214.32	5.422%	$225.9404	$225.94	$225.95	$225.90
Purchase #3	$180.99	6.399%	$192.5716	$192.57	$192.55	$192.60
Purchase #4	$173.35	6.186%	$184.0734	$184.07	$184.05	$184.10
Purchase #5	$187.87	13.700%	$213.6082	$213.61	$213.60	$213.60
Purchase #6	$105.28	11.667%	$117.563	$117.56	$117.55	$117.60
Purchase #7	$62.78	6.223%	$66.6868	$66.69	$66.70	$66.70
7 purchase totals =	$1,015.20		$1,098.8957	$1,098.89	$1,098.85	$1,099.00