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	$202.88	6.401%	$215.8663	$215.87	$215.85	$215.90
Purchase #2	$97.51	12.637%	$109.8323	$109.83	$109.85	$109.80
Purchase #3	$152.94	4.269%	$159.469	$159.47	$159.45	$159.50
Purchase #4	$154.98	7.233%	$166.1897	$166.19	$166.20	$166.20
Purchase #5	$111.77	11.294%	$124.3933	$124.39	$124.40	$124.40
Purchase #6	$156.50	13.429%	$177.5164	$177.52	$177.50	$177.50
Purchase #7	$60.32	4.444%	$63.0006	$63.00	$63.00	$63.00
7 purchase totals =	$936.90		$1,016.2676	$1,016.27	$1,016.25	$1,016.30