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	$196.85	3.388%	$203.5193	$203.52	$203.50	$203.50
Purchase #2	$154.40	8.351%	$167.2939	$167.29	$167.30	$167.30
Purchase #3	$18.99	12.569%	$21.3769	$21.38	$21.40	$21.40
Purchase #4	$70.55	11.209%	$78.4579	$78.46	$78.45	$78.50
Purchase #5	$144.58	4.244%	$150.716	$150.72	$150.70	$150.70
Purchase #6	$214.73	4.324%	$224.0149	$224.01	$224.00	$224.00
Purchase #7	$219.50	5.660%	$231.9237	$231.92	$231.90	$231.90
7 purchase totals =	$1,019.60		$1,077.3026	$1,077.30	$1,077.25	$1,077.30