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	$178.64	12.276%	$200.5698	$200.57	$200.55	$200.60
Purchase #2	$250.36	4.750%	$262.2521	$262.25	$262.25	$262.30
Purchase #3	$239.95	13.382%	$272.0601	$272.06	$272.05	$272.10
Purchase #4	$135.41	12.874%	$152.8427	$152.84	$152.85	$152.80
Purchase #5	$126.89	13.548%	$144.0811	$144.08	$144.10	$144.10
Purchase #6	$143.29	3.719%	$148.619	$148.62	$148.60	$148.60
Purchase #7	$179.80	3.105%	$185.3828	$185.38	$185.40	$185.40
7 purchase totals =	$1,254.34		$1,365.8076	$1,365.80	$1,365.80	$1,365.90