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	$236.67	7.126%	$253.5351	$253.54	$253.55	$253.50
Purchase #2	$146.88	12.275%	$164.9095	$164.91	$164.90	$164.90
Purchase #3	$130.39	9.746%	$143.0978	$143.10	$143.10	$143.10
Purchase #4	$9.40	10.713%	$10.407	$10.41	$10.40	$10.40
Purchase #5	$244.71	3.575%	$253.4584	$253.46	$253.45	$253.50
Purchase #6	$132.52	13.597%	$150.5387	$150.54	$150.55	$150.50
Purchase #7	$127.66	11.721%	$142.623	$142.62	$142.60	$142.60
7 purchase totals =	$1,028.23		$1,118.5695	$1,118.58	$1,118.55	$1,118.50