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	$139.39	12.295%	$156.528	$156.53	$156.55	$156.50
Purchase #2	$117.73	10.638%	$130.2541	$130.25	$130.25	$130.30
Purchase #3	$137.70	9.372%	$150.6052	$150.61	$150.60	$150.60
Purchase #4	$117.81	5.189%	$123.9232	$123.92	$123.90	$123.90
Purchase #5	$225.43	12.397%	$253.3766	$253.38	$253.40	$253.40
Purchase #6	$187.81	3.685%	$194.7308	$194.73	$194.75	$194.70
Purchase #7	$34.47	5.270%	$36.2866	$36.29	$36.30	$36.30
7 purchase totals =	$960.34		$1,045.7045	$1,045.71	$1,045.75	$1,045.70