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	$207.68	4.125%	$216.2468	$216.25	$216.25	$216.20
Purchase #2	$35.85	11.169%	$39.8541	$39.85	$39.85	$39.90
Purchase #3	$166.89	7.567%	$179.5186	$179.52	$179.50	$179.50
Purchase #4	$109.38	9.642%	$119.9264	$119.93	$119.95	$119.90
Purchase #5	$47.78	13.555%	$54.2566	$54.26	$54.25	$54.30
Purchase #6	$226.67	12.724%	$255.5115	$255.51	$255.50	$255.50
Purchase #7	$96.38	6.278%	$102.4307	$102.43	$102.45	$102.40
7 purchase totals =	$890.63		$967.7447	$967.75	$967.75	$967.70