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	$148.86	9.661%	$163.2414	$163.24	$163.25	$163.20
Purchase #2	$101.38	3.212%	$104.6363	$104.64	$104.65	$104.60
Purchase #3	$85.70	5.607%	$90.5052	$90.51	$90.50	$90.50
Purchase #4	$90.25	10.287%	$99.534	$99.53	$99.55	$99.50
Purchase #5	$117.72	8.802%	$128.0817	$128.08	$128.10	$128.10
Purchase #6	$40.78	9.362%	$44.5978	$44.60	$44.60	$44.60
Purchase #7	$227.58	5.520%	$240.1424	$240.14	$240.15	$240.10
7 purchase totals =	$812.27		$870.7388	$870.74	$870.80	$870.60