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	$98.81	7.249%	$105.9727	$105.97	$105.95	$106.00
Purchase #2	$203.27	8.764%	$221.0846	$221.08	$221.10	$221.10
Purchase #3	$84.97	6.371%	$90.3834	$90.38	$90.40	$90.40
Purchase #4	$60.59	10.208%	$66.775	$66.78	$66.80	$66.80
Purchase #5	$172.53	13.379%	$195.6128	$195.61	$195.60	$195.60
Purchase #6	$111.60	4.380%	$116.4881	$116.49	$116.50	$116.50
Purchase #7	$91.84	12.102%	$102.9545	$102.95	$102.95	$103.00
7 purchase totals =	$823.61		$899.2711	$899.26	$899.30	$899.40