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	$151.70	9.726%	$166.4543	$166.45	$166.45	$166.50
Purchase #2	$103.47	11.679%	$115.5543	$115.55	$115.55	$115.60
Purchase #3	$74.64	9.493%	$81.7256	$81.73	$81.75	$81.70
Purchase #4	$173.81	9.786%	$190.819	$190.82	$190.80	$190.80
Purchase #5	$182.88	9.695%	$200.6102	$200.61	$200.60	$200.60
Purchase #6	$144.78	8.154%	$156.5854	$156.59	$156.60	$156.60
Purchase #7	$245.75	5.638%	$259.6054	$259.61	$259.60	$259.60
7 purchase totals =	$1,077.03		$1,171.3542	$1,171.36	$1,171.35	$1,171.40