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	$182.78	9.376%	$199.9175	$199.92	$199.90	$199.90
Purchase #2	$183.25	3.781%	$190.1787	$190.18	$190.20	$190.20
Purchase #3	$8.82	4.716%	$9.236	$9.24	$9.25	$9.20
Purchase #4	$218.45	10.669%	$241.7564	$241.76	$241.75	$241.80
Purchase #5	$100.76	3.583%	$104.3702	$104.37	$104.35	$104.40
Purchase #6	$111.61	10.227%	$123.0244	$123.02	$123.00	$123.00
Purchase #7	$208.94	10.731%	$231.3614	$231.36	$231.35	$231.40
7 purchase totals =	$1,014.61		$1,099.8446	$1,099.85	$1,099.80	$1,099.90