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	$173.60	13.252%	$196.6055	$196.61	$196.60	$196.60
Purchase #2	$100.81	4.671%	$105.5188	$105.52	$105.50	$105.50
Purchase #3	$197.47	12.102%	$221.3678	$221.37	$221.35	$221.40
Purchase #4	$37.49	7.854%	$40.4345	$40.43	$40.45	$40.40
Purchase #5	$8.89	10.345%	$9.8097	$9.81	$9.80	$9.80
Purchase #6	$244.45	8.115%	$264.2871	$264.29	$264.30	$264.30
Purchase #7	$216.32	7.201%	$231.8972	$231.90	$231.90	$231.90
7 purchase totals =	$979.03		$1,069.9206	$1,069.93	$1,069.90	$1,069.90