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	$40.26	13.236%	$45.5888	$45.59	$45.60	$45.60
Purchase #2	$51.93	13.718%	$59.0538	$59.05	$59.05	$59.10
Purchase #3	$22.50	4.460%	$23.5035	$23.50	$23.50	$23.50
Purchase #4	$250.26	7.646%	$269.3949	$269.39	$269.40	$269.40
Purchase #5	$10.78	10.800%	$11.9442	$11.94	$11.95	$11.90
Purchase #6	$132.83	3.425%	$137.3794	$137.38	$137.40	$137.40
Purchase #7	$181.61	4.821%	$190.3654	$190.37	$190.35	$190.40
7 purchase totals =	$690.17		$737.2300	$737.22	$737.25	$737.30