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	$100.52	11.325%	$111.9039	$111.90	$111.90	$111.90
Purchase #2	$123.80	6.577%	$131.9423	$131.94	$131.95	$131.90
Purchase #3	$45.62	5.380%	$48.0744	$48.07	$48.05	$48.10
Purchase #4	$143.52	11.167%	$159.5469	$159.55	$159.55	$159.50
Purchase #5	$200.61	12.128%	$224.94	$224.94	$224.95	$224.90
Purchase #6	$162.39	7.191%	$174.0675	$174.07	$174.05	$174.10
Purchase #7	$206.61	10.640%	$228.5933	$228.59	$228.60	$228.60
7 purchase totals =	$983.07		$1,079.0683	$1,079.06	$1,079.05	$1,079.00