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	$103.54	7.715%	$111.5281	$111.53	$111.55	$111.50
Purchase #2	$234.57	13.203%	$265.5403	$265.54	$265.55	$265.50
Purchase #3	$129.93	4.548%	$135.8392	$135.84	$135.85	$135.80
Purchase #4	$79.96	12.156%	$89.6799	$89.68	$89.70	$89.70
Purchase #5	$46.61	10.741%	$51.6164	$51.62	$51.60	$51.60
Purchase #6	$238.49	12.526%	$268.3633	$268.36	$268.35	$268.40
Purchase #7	$165.80	6.387%	$176.3896	$176.39	$176.40	$176.40
7 purchase totals =	$998.90		$1,098.9568	$1,098.96	$1,099.00	$1,098.90