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	$192.32	6.606%	$205.0247	$205.02	$205.00	$205.00
Purchase #2	$62.63	6.236%	$66.5356	$66.54	$66.55	$66.50
Purchase #3	$248.57	5.336%	$261.8337	$261.83	$261.85	$261.80
Purchase #4	$91.83	5.641%	$97.0101	$97.01	$97.00	$97.00
Purchase #5	$103.83	7.481%	$111.5975	$111.60	$111.60	$111.60
Purchase #6	$58.50	7.823%	$63.0765	$63.08	$63.10	$63.10
Purchase #7	$104.51	6.767%	$111.5822	$111.58	$111.60	$111.60
7 purchase totals =	$862.19		$916.6603	$916.66	$916.70	$916.60