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	$103.68	7.300%	$111.2486	$111.25	$111.25	$111.20
Purchase #2	$131.40	9.352%	$143.6885	$143.69	$143.70	$143.70
Purchase #3	$21.26	9.810%	$23.3456	$23.35	$23.35	$23.30
Purchase #4	$33.43	13.113%	$37.8137	$37.81	$37.80	$37.80
Purchase #5	$116.43	13.712%	$132.3949	$132.39	$132.40	$132.40
Purchase #6	$137.72	3.128%	$142.0279	$142.03	$142.05	$142.00
Purchase #7	$145.91	6.506%	$155.4029	$155.40	$155.40	$155.40
7 purchase totals =	$689.83		$745.9221	$745.92	$745.95	$745.80