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	$132.41	5.725%	$139.9905	$139.99	$140.00	$140.00
Purchase #2	$78.82	4.640%	$82.4772	$82.48	$82.50	$82.50
Purchase #3	$66.35	4.687%	$69.4598	$69.46	$69.45	$69.50
Purchase #4	$52.69	13.356%	$59.7273	$59.73	$59.75	$59.70
Purchase #5	$226.69	12.581%	$255.2099	$255.21	$255.20	$255.20
Purchase #6	$201.91	6.125%	$214.277	$214.28	$214.30	$214.30
Purchase #7	$250.74	6.241%	$266.3887	$266.39	$266.40	$266.40
7 purchase totals =	$1,009.61		$1,087.5304	$1,087.54	$1,087.60	$1,087.60