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	$112.78	9.863%	$123.9035	$123.90	$123.90	$123.90
Purchase #2	$26.77	8.646%	$29.0845	$29.08	$29.10	$29.10
Purchase #3	$115.48	6.852%	$123.3927	$123.39	$123.40	$123.40
Purchase #4	$225.27	13.739%	$256.2198	$256.22	$256.20	$256.20
Purchase #5	$241.72	3.565%	$250.3373	$250.34	$250.35	$250.30
Purchase #6	$128.65	9.331%	$140.6543	$140.65	$140.65	$140.70
Purchase #7	$146.44	8.379%	$158.7102	$158.71	$158.70	$158.70
7 purchase totals =	$997.11		$1,082.3023	$1,082.29	$1,082.30	$1,082.30