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	$185.45	6.181%	$196.9127	$196.91	$196.90	$196.90
Purchase #2	$112.31	4.433%	$117.2887	$117.29	$117.30	$117.30
Purchase #3	$207.85	5.179%	$218.6146	$218.61	$218.60	$218.60
Purchase #4	$177.83	10.538%	$196.5697	$196.57	$196.55	$196.60
Purchase #5	$34.44	12.716%	$38.8194	$38.82	$38.80	$38.80
Purchase #6	$102.29	4.322%	$106.711	$106.71	$106.70	$106.70
Purchase #7	$158.64	11.246%	$176.4807	$176.48	$176.50	$176.50
7 purchase totals =	$978.81		$1,051.3968	$1,051.39	$1,051.35	$1,051.40