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	$100.88	6.337%	$107.2728	$107.27	$107.25	$107.30
Purchase #2	$205.45	8.836%	$223.6036	$223.60	$223.60	$223.60
Purchase #3	$75.43	13.591%	$85.6817	$85.68	$85.70	$85.70
Purchase #4	$226.29	12.747%	$255.1352	$255.14	$255.15	$255.10
Purchase #5	$128.75	4.501%	$134.545	$134.55	$134.55	$134.50
Purchase #6	$198.69	13.674%	$225.8589	$225.86	$225.85	$225.90
Purchase #7	$21.63	13.415%	$24.5317	$24.53	$24.55	$24.50
7 purchase totals =	$957.12		$1,056.6289	$1,056.63	$1,056.65	$1,056.60