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	$238.47	5.441%	$251.4452	$251.45	$251.45	$251.40
Purchase #2	$128.44	12.177%	$144.0801	$144.08	$144.10	$144.10
Purchase #3	$175.51	8.328%	$190.1265	$190.13	$190.15	$190.10
Purchase #4	$88.75	13.634%	$100.8502	$100.85	$100.85	$100.90
Purchase #5	$64.25	4.158%	$66.9215	$66.92	$66.90	$66.90
Purchase #6	$248.54	4.838%	$260.5644	$260.56	$260.55	$260.60
Purchase #7	$132.83	5.827%	$140.57	$140.57	$140.55	$140.60
7 purchase totals =	$1,076.79		$1,154.5579	$1,154.56	$1,154.55	$1,154.60