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	$134.59	7.536%	$144.7327	$144.73	$144.75	$144.70
Purchase #2	$27.54	8.628%	$29.9162	$29.92	$29.90	$29.90
Purchase #3	$214.82	5.143%	$225.8682	$225.87	$225.85	$225.90
Purchase #4	$122.32	13.750%	$139.139	$139.14	$139.15	$139.10
Purchase #5	$117.87	9.205%	$128.7199	$128.72	$128.70	$128.70
Purchase #6	$93.55	12.810%	$105.5338	$105.53	$105.55	$105.50
Purchase #7	$224.38	8.436%	$243.3087	$243.31	$243.30	$243.30
7 purchase totals =	$935.07		$1,017.2185	$1,017.22	$1,017.20	$1,017.10