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	$214.26	11.821%	$239.5877	$239.59	$239.60	$239.60
Purchase #2	$66.59	4.823%	$69.8016	$69.80	$69.80	$69.80
Purchase #3	$189.84	3.438%	$196.3667	$196.37	$196.35	$196.40
Purchase #4	$127.38	13.579%	$144.6769	$144.68	$144.70	$144.70
Purchase #5	$177.69	3.797%	$184.4369	$184.44	$184.45	$184.40
Purchase #6	$119.43	3.488%	$123.5957	$123.60	$123.60	$123.60
Purchase #7	$143.43	7.749%	$154.5444	$154.54	$154.55	$154.50
7 purchase totals =	$1,038.62		$1,113.0099	$1,113.02	$1,113.05	$1,113.00