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	$216.47	3.863%	$224.8322	$224.83	$224.85	$224.80
Purchase #2	$38.49	10.549%	$42.5503	$42.55	$42.55	$42.60
Purchase #3	$165.65	12.715%	$186.7124	$186.71	$186.70	$186.70
Purchase #4	$107.37	6.257%	$114.0881	$114.09	$114.10	$114.10
Purchase #5	$223.33	3.665%	$231.515	$231.52	$231.50	$231.50
Purchase #6	$127.45	13.527%	$144.6902	$144.69	$144.70	$144.70
Purchase #7	$134.53	6.550%	$143.3417	$143.34	$143.35	$143.30
7 purchase totals =	$1,013.29		$1,087.7299	$1,087.73	$1,087.75	$1,087.70