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	$196.87	4.158%	$205.0559	$205.06	$205.05	$205.10
Purchase #2	$99.41	12.467%	$111.8034	$111.80	$111.80	$111.80
Purchase #3	$194.92	12.156%	$218.6145	$218.61	$218.60	$218.60
Purchase #4	$27.82	10.769%	$30.8159	$30.82	$30.80	$30.80
Purchase #5	$132.87	8.679%	$144.4018	$144.40	$144.40	$144.40
Purchase #6	$250.86	3.177%	$258.8298	$258.83	$258.85	$258.80
Purchase #7	$137.97	10.846%	$152.9342	$152.93	$152.95	$152.90
7 purchase totals =	$1,040.72		$1,122.4555	$1,122.45	$1,122.45	$1,122.40