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	$192.70	4.260%	$200.909	$200.91	$200.90	$200.90
Purchase #2	$111.96	3.619%	$116.0118	$116.01	$116.00	$116.00
Purchase #3	$79.34	10.233%	$87.4589	$87.46	$87.45	$87.50
Purchase #4	$54.32	9.672%	$59.5738	$59.57	$59.55	$59.60
Purchase #5	$104.50	10.835%	$115.8226	$115.82	$115.80	$115.80
Purchase #6	$82.25	8.841%	$89.5217	$89.52	$89.50	$89.50
Purchase #7	$246.51	5.783%	$260.7657	$260.77	$260.75	$260.80
7 purchase totals =	$871.58		$930.0635	$930.06	$929.95	$930.10