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	$88.48	13.676%	$100.5805	$100.58	$100.60	$100.60
Purchase #2	$117.94	4.864%	$123.6766	$123.68	$123.70	$123.70
Purchase #3	$38.83	9.676%	$42.5872	$42.59	$42.60	$42.60
Purchase #4	$159.26	5.333%	$167.7533	$167.75	$167.75	$167.80
Purchase #5	$114.72	5.461%	$120.9849	$120.98	$121.00	$121.00
Purchase #6	$189.81	3.864%	$197.1443	$197.14	$197.15	$197.10
Purchase #7	$103.55	12.522%	$116.5165	$116.52	$116.50	$116.50
7 purchase totals =	$812.59		$869.2433	$869.24	$869.30	$869.30