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	$72.59	13.273%	$82.2249	$82.22	$82.20	$82.20
Purchase #2	$176.92	12.393%	$198.8457	$198.85	$198.85	$198.80
Purchase #3	$192.73	4.244%	$200.9095	$200.91	$200.90	$200.90
Purchase #4	$188.54	5.734%	$199.3509	$199.35	$199.35	$199.40
Purchase #5	$233.77	5.485%	$246.5923	$246.59	$246.60	$246.60
Purchase #6	$200.88	10.701%	$222.3762	$222.38	$222.40	$222.40
Purchase #7	$172.58	5.141%	$181.4523	$181.45	$181.45	$181.50
7 purchase totals =	$1,238.01		$1,331.7518	$1,331.75	$1,331.75	$1,331.80