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	$10.92	9.418%	$11.9484	$11.95	$11.95	$11.90
Purchase #2	$23.31	6.773%	$24.8888	$24.89	$24.90	$24.90
Purchase #3	$184.43	8.493%	$200.0936	$200.09	$200.10	$200.10
Purchase #4	$181.43	13.223%	$205.4205	$205.42	$205.40	$205.40
Purchase #5	$97.25	8.155%	$105.1807	$105.18	$105.20	$105.20
Purchase #6	$139.48	13.196%	$157.8858	$157.89	$157.90	$157.90
Purchase #7	$149.64	4.581%	$156.495	$156.50	$156.50	$156.50
7 purchase totals =	$786.46		$861.9128	$861.92	$861.95	$861.90