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	$158.69	4.284%	$165.4883	$165.49	$165.50	$165.50
Purchase #2	$86.93	4.200%	$90.5811	$90.58	$90.60	$90.60
Purchase #3	$97.87	6.431%	$104.164	$104.16	$104.15	$104.20
Purchase #4	$73.82	10.257%	$81.3917	$81.39	$81.40	$81.40
Purchase #5	$192.51	13.493%	$218.4854	$218.49	$218.50	$218.50
Purchase #6	$112.42	6.208%	$119.399	$119.40	$119.40	$119.40
Purchase #7	$178.35	4.258%	$185.9441	$185.94	$185.95	$185.90
7 purchase totals =	$900.59		$965.4536	$965.45	$965.50	$965.50