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	$244.72	8.421%	$265.3279	$265.33	$265.35	$265.30
Purchase #2	$219.80	12.411%	$247.0794	$247.08	$247.10	$247.10
Purchase #3	$133.68	5.537%	$141.0819	$141.08	$141.10	$141.10
Purchase #4	$197.96	10.267%	$218.2846	$218.28	$218.30	$218.30
Purchase #5	$104.47	9.617%	$114.5169	$114.52	$114.50	$114.50
Purchase #6	$86.70	3.781%	$89.9781	$89.98	$90.00	$90.00
Purchase #7	$37.87	6.259%	$40.2403	$40.24	$40.25	$40.20
7 purchase totals =	$1,025.20		$1,116.5091	$1,116.51	$1,116.60	$1,116.50