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	$216.48	3.249%	$223.5134	$223.51	$223.50	$223.50
Purchase #2	$36.40	10.423%	$40.194	$40.19	$40.20	$40.20
Purchase #3	$28.67	3.472%	$29.6654	$29.67	$29.65	$29.70
Purchase #4	$165.72	5.571%	$174.9523	$174.95	$174.95	$175.00
Purchase #5	$241.84	8.581%	$262.5923	$262.59	$262.60	$262.60
Purchase #6	$98.59	13.854%	$112.2487	$112.25	$112.25	$112.20
Purchase #7	$237.92	7.643%	$256.1042	$256.10	$256.10	$256.10
7 purchase totals =	$1,025.62		$1,099.2703	$1,099.26	$1,099.25	$1,099.30