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	$106.92	5.862%	$113.1877	$113.19	$113.20	$113.20
Purchase #2	$166.57	5.695%	$176.0562	$176.06	$176.05	$176.10
Purchase #3	$163.63	5.480%	$172.5969	$172.60	$172.60	$172.60
Purchase #4	$107.43	4.177%	$111.9174	$111.92	$111.90	$111.90
Purchase #5	$196.38	9.298%	$214.6394	$214.64	$214.65	$214.60
Purchase #6	$180.65	10.837%	$200.227	$200.23	$200.25	$200.20
Purchase #7	$144.94	4.386%	$151.2971	$151.30	$151.30	$151.30
7 purchase totals =	$1,066.52		$1,139.9217	$1,139.94	$1,139.95	$1,139.90