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	$206.29	12.242%	$231.544	$231.54	$231.55	$231.50
Purchase #2	$190.64	4.167%	$198.584	$198.58	$198.60	$198.60
Purchase #3	$186.64	4.176%	$194.4341	$194.43	$194.45	$194.40
Purchase #4	$189.52	5.716%	$200.353	$200.35	$200.35	$200.40
Purchase #5	$87.83	6.294%	$93.358	$93.36	$93.35	$93.40
Purchase #6	$175.43	4.748%	$183.7594	$183.76	$183.75	$183.80
Purchase #7	$82.76	9.401%	$90.5403	$90.54	$90.55	$90.50
7 purchase totals =	$1,119.11		$1,192.5728	$1,192.56	$1,192.60	$1,192.60