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	$238.37	4.761%	$249.7188	$249.72	$249.70	$249.70
Purchase #2	$177.40	8.667%	$192.7753	$192.78	$192.80	$192.80
Purchase #3	$112.40	4.535%	$117.4973	$117.50	$117.50	$117.50
Purchase #4	$178.30	9.143%	$194.602	$194.60	$194.60	$194.60
Purchase #5	$111.35	4.761%	$116.6514	$116.65	$116.65	$116.70
Purchase #6	$196.92	6.428%	$209.578	$209.58	$209.60	$209.60
Purchase #7	$116.53	10.110%	$128.3112	$128.31	$128.30	$128.30
7 purchase totals =	$1,131.27		$1,209.1340	$1,209.14	$1,209.15	$1,209.20