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	$120.60	9.218%	$131.7169	$131.72	$131.70	$131.70
Purchase #2	$133.36	9.769%	$146.3879	$146.39	$146.40	$146.40
Purchase #3	$172.86	4.807%	$181.1694	$181.17	$181.15	$181.20
Purchase #4	$171.31	9.202%	$187.0739	$187.07	$187.05	$187.10
Purchase #5	$123.31	13.107%	$139.4722	$139.47	$139.45	$139.50
Purchase #6	$195.52	11.546%	$218.0947	$218.09	$218.10	$218.10
Purchase #7	$39.95	13.827%	$45.4739	$45.47	$45.45	$45.50
7 purchase totals =	$956.91		$1,049.3889	$1,049.38	$1,049.30	$1,049.50