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	$168.98	11.445%	$188.3198	$188.32	$188.30	$188.30
Purchase #2	$102.56	13.481%	$116.3861	$116.39	$116.40	$116.40
Purchase #3	$222.92	6.116%	$236.5538	$236.55	$236.55	$236.60
Purchase #4	$70.45	5.526%	$74.3431	$74.34	$74.35	$74.30
Purchase #5	$172.59	3.354%	$178.3787	$178.38	$178.40	$178.40
Purchase #6	$155.52	4.549%	$162.5946	$162.59	$162.60	$162.60
Purchase #7	$122.93	4.509%	$128.4729	$128.47	$128.45	$128.50
7 purchase totals =	$1,015.95		$1,085.0490	$1,085.04	$1,085.05	$1,085.10