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	$200.80	11.685%	$224.2635	$224.26	$224.25	$224.30
Purchase #2	$71.47	9.155%	$78.0131	$78.01	$78.00	$78.00
Purchase #3	$57.92	8.436%	$62.8061	$62.81	$62.80	$62.80
Purchase #4	$248.94	4.549%	$260.2643	$260.26	$260.25	$260.30
Purchase #5	$207.33	13.640%	$235.6098	$235.61	$235.60	$235.60
Purchase #6	$155.60	3.769%	$161.4646	$161.46	$161.45	$161.50
Purchase #7	$160.51	8.328%	$173.8773	$173.88	$173.90	$173.90
7 purchase totals =	$1,102.57		$1,196.2987	$1,196.29	$1,196.25	$1,196.40