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	$51.94	4.405%	$54.228	$54.23	$54.25	$54.20
Purchase #2	$90.42	13.195%	$102.3509	$102.35	$102.35	$102.40
Purchase #3	$20.68	4.334%	$21.5763	$21.58	$21.60	$21.60
Purchase #4	$209.87	7.546%	$225.7068	$225.71	$225.70	$225.70
Purchase #5	$139.55	8.641%	$151.6085	$151.61	$151.60	$151.60
Purchase #6	$95.99	5.763%	$101.5219	$101.52	$101.50	$101.50
Purchase #7	$113.38	5.162%	$119.2327	$119.23	$119.25	$119.20
7 purchase totals =	$721.83		$776.2251	$776.23	$776.25	$776.20