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	$230.86	7.142%	$247.348	$247.35	$247.35	$247.30
Purchase #2	$155.42	10.352%	$171.5091	$171.51	$171.50	$171.50
Purchase #3	$50.43	5.698%	$53.3035	$53.30	$53.30	$53.30
Purchase #4	$140.86	11.601%	$157.2012	$157.20	$157.20	$157.20
Purchase #5	$152.78	7.728%	$164.5868	$164.59	$164.60	$164.60
Purchase #6	$49.67	8.334%	$53.8095	$53.81	$53.80	$53.80
Purchase #7	$122.83	13.839%	$139.8284	$139.83	$139.85	$139.80
7 purchase totals =	$902.85		$987.5865	$987.59	$987.60	$987.50