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	$206.81	4.252%	$215.6036	$215.60	$215.60	$215.60
Purchase #2	$33.75	11.608%	$37.6677	$37.67	$37.65	$37.70
Purchase #3	$158.52	11.440%	$176.6547	$176.65	$176.65	$176.70
Purchase #4	$145.51	13.351%	$164.937	$164.94	$164.95	$164.90
Purchase #5	$106.68	4.855%	$111.8593	$111.86	$111.85	$111.90
Purchase #6	$69.52	6.470%	$74.0179	$74.02	$74.00	$74.00
Purchase #7	$226.73	12.838%	$255.8376	$255.84	$255.85	$255.80
7 purchase totals =	$947.52		$1,036.5778	$1,036.58	$1,036.55	$1,036.60