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	$42.79	13.161%	$48.4216	$48.42	$48.40	$48.40
Purchase #2	$242.30	4.373%	$252.8958	$252.90	$252.90	$252.90
Purchase #3	$25.86	11.545%	$28.8455	$28.85	$28.85	$28.80
Purchase #4	$98.29	6.447%	$104.6268	$104.63	$104.65	$104.60
Purchase #5	$121.63	4.103%	$126.6205	$126.62	$126.60	$126.60
Purchase #6	$182.26	7.713%	$196.3177	$196.32	$196.30	$196.30
Purchase #7	$244.89	5.773%	$259.0275	$259.03	$259.05	$259.00
7 purchase totals =	$958.02		$1,016.7554	$1,016.77	$1,016.75	$1,016.60