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	$108.91	6.146%	$115.6036	$115.60	$115.60	$115.60
Purchase #2	$241.39	9.560%	$264.4669	$264.47	$264.45	$264.50
Purchase #3	$105.45	5.827%	$111.5946	$111.59	$111.60	$111.60
Purchase #4	$106.74	12.388%	$119.963	$119.96	$119.95	$120.00
Purchase #5	$94.78	5.761%	$100.2403	$100.24	$100.25	$100.20
Purchase #6	$190.53	9.202%	$208.0626	$208.06	$208.05	$208.10
Purchase #7	$160.55	10.129%	$176.8121	$176.81	$176.80	$176.80
7 purchase totals =	$1,008.35		$1,096.7431	$1,096.73	$1,096.70	$1,096.80