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	$105.95	12.630%	$119.3315	$119.33	$119.35	$119.30
Purchase #2	$101.88	3.130%	$105.0688	$105.07	$105.05	$105.10
Purchase #3	$103.83	8.431%	$112.5839	$112.58	$112.60	$112.60
Purchase #4	$21.54	12.198%	$24.1674	$24.17	$24.15	$24.20
Purchase #5	$119.61	5.754%	$126.4924	$126.49	$126.50	$126.50
Purchase #6	$236.82	3.389%	$244.8458	$244.85	$244.85	$244.80
Purchase #7	$133.39	12.825%	$150.4973	$150.50	$150.50	$150.50
7 purchase totals =	$823.02		$882.9871	$882.99	$883.00	$883.00