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	$212.52	3.231%	$219.3865	$219.39	$219.40	$219.40
Purchase #2	$52.96	5.591%	$55.921	$55.92	$55.90	$55.90
Purchase #3	$107.31	4.714%	$112.3686	$112.37	$112.35	$112.40
Purchase #4	$196.58	8.869%	$214.0147	$214.01	$214.00	$214.00
Purchase #5	$231.95	13.363%	$262.9455	$262.95	$262.95	$262.90
Purchase #6	$183.93	9.218%	$200.8847	$200.88	$200.90	$200.90
Purchase #7	$18.99	10.150%	$20.9175	$20.92	$20.90	$20.90
7 purchase totals =	$1,004.24		$1,086.4385	$1,086.44	$1,086.40	$1,086.40