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	$190.78	5.329%	$200.9467	$200.95	$200.95	$200.90
Purchase #2	$34.28	13.304%	$38.8406	$38.84	$38.85	$38.80
Purchase #3	$23.35	6.500%	$24.8678	$24.87	$24.85	$24.90
Purchase #4	$11.89	3.378%	$12.2916	$12.29	$12.30	$12.30
Purchase #5	$210.73	5.636%	$222.6067	$222.61	$222.60	$222.60
Purchase #6	$208.75	10.738%	$231.1656	$231.17	$231.15	$231.20
Purchase #7	$143.97	11.727%	$160.8534	$160.85	$160.85	$160.90
7 purchase totals =	$823.75		$891.5724	$891.58	$891.55	$891.60