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	$206.37	11.695%	$230.505	$230.51	$230.50	$230.50
Purchase #2	$176.77	6.659%	$188.5411	$188.54	$188.55	$188.50
Purchase #3	$111.66	12.302%	$125.3964	$125.40	$125.40	$125.40
Purchase #4	$155.25	7.217%	$166.4544	$166.45	$166.45	$166.50
Purchase #5	$42.90	13.388%	$48.6435	$48.64	$48.65	$48.60
Purchase #6	$107.50	3.810%	$111.5958	$111.60	$111.60	$111.60
Purchase #7	$163.55	9.860%	$179.676	$179.68	$179.70	$179.70
7 purchase totals =	$964.00		$1,050.8122	$1,050.82	$1,050.85	$1,050.80