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	$115.97	6.203%	$123.1636	$123.16	$123.15	$123.20
Purchase #2	$21.46	4.719%	$22.4727	$22.47	$22.45	$22.50
Purchase #3	$140.70	11.283%	$156.5752	$156.58	$156.60	$156.60
Purchase #4	$66.85	5.668%	$70.6391	$70.64	$70.65	$70.60
Purchase #5	$100.38	11.354%	$111.7771	$111.78	$111.80	$111.80
Purchase #6	$211.40	9.438%	$231.3519	$231.35	$231.35	$231.40
Purchase #7	$12.85	9.505%	$14.0714	$14.07	$14.05	$14.10
7 purchase totals =	$669.61		$730.0510	$730.05	$730.05	$730.20