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	$240.67	9.158%	$262.7106	$262.71	$262.70	$262.70
Purchase #2	$77.89	13.758%	$88.6061	$88.61	$88.60	$88.60
Purchase #3	$81.94	4.635%	$85.7379	$85.74	$85.75	$85.70
Purchase #4	$141.51	12.185%	$158.753	$158.75	$158.75	$158.80
Purchase #5	$236.32	11.262%	$262.9344	$262.93	$262.95	$262.90
Purchase #6	$80.71	9.847%	$88.6575	$88.66	$88.65	$88.70
Purchase #7	$66.59	6.398%	$70.8504	$70.85	$70.85	$70.90
7 purchase totals =	$925.63		$1,018.2499	$1,018.25	$1,018.25	$1,018.30