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	$170.81	8.361%	$185.0914	$185.09	$185.10	$185.10
Purchase #2	$21.88	9.546%	$23.9687	$23.97	$23.95	$24.00
Purchase #3	$125.64	11.448%	$140.0233	$140.02	$140.00	$140.00
Purchase #4	$199.53	7.318%	$214.1316	$214.13	$214.15	$214.10
Purchase #5	$179.88	4.242%	$187.5105	$187.51	$187.50	$187.50
Purchase #6	$235.70	8.140%	$254.886	$254.89	$254.90	$254.90
Purchase #7	$168.49	13.275%	$190.857	$190.86	$190.85	$190.90
7 purchase totals =	$1,101.93		$1,196.4685	$1,196.47	$1,196.45	$1,196.50