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	$22.83	12.852%	$25.7641	$25.76	$25.75	$25.80
Purchase #2	$187.28	13.307%	$212.2013	$212.20	$212.20	$212.20
Purchase #3	$65.76	10.419%	$72.6115	$72.61	$72.60	$72.60
Purchase #4	$108.51	4.762%	$113.6772	$113.68	$113.70	$113.70
Purchase #5	$119.40	6.123%	$126.7109	$126.71	$126.70	$126.70
Purchase #6	$237.90	7.236%	$255.1144	$255.11	$255.10	$255.10
Purchase #7	$242.61	13.304%	$274.8868	$274.89	$274.90	$274.90
7 purchase totals =	$984.29		$1,080.9662	$1,080.96	$1,080.95	$1,081.00