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	$108.27	7.436%	$116.321	$116.32	$116.30	$116.30
Purchase #2	$13.40	9.222%	$14.6357	$14.64	$14.65	$14.60
Purchase #3	$91.45	13.263%	$103.579	$103.58	$103.60	$103.60
Purchase #4	$55.95	10.225%	$61.6709	$61.67	$61.65	$61.70
Purchase #5	$155.83	6.363%	$165.7455	$165.75	$165.75	$165.70
Purchase #6	$209.79	10.359%	$231.5221	$231.52	$231.50	$231.50
Purchase #7	$104.80	4.385%	$109.3955	$109.40	$109.40	$109.40
7 purchase totals =	$739.49		$802.8697	$802.88	$802.85	$802.80