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	$131.59	4.131%	$137.026	$137.03	$137.05	$137.00
Purchase #2	$202.42	8.355%	$219.3322	$219.33	$219.35	$219.30
Purchase #3	$203.85	8.668%	$221.5197	$221.52	$221.50	$221.50
Purchase #4	$112.78	6.807%	$120.4569	$120.46	$120.45	$120.50
Purchase #5	$225.60	12.833%	$254.5512	$254.55	$254.55	$254.60
Purchase #6	$72.45	12.871%	$81.775	$81.78	$81.80	$81.80
Purchase #7	$70.72	3.105%	$72.9159	$72.92	$72.90	$72.90
7 purchase totals =	$1,019.41		$1,107.5769	$1,107.59	$1,107.60	$1,107.60