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	$216.35	7.504%	$232.5849	$232.58	$232.60	$232.60
Purchase #2	$78.91	3.124%	$81.3751	$81.38	$81.40	$81.40
Purchase #3	$90.36	9.374%	$98.8303	$98.83	$98.85	$98.80
Purchase #4	$150.56	5.393%	$158.6797	$158.68	$158.70	$158.70
Purchase #5	$106.47	3.103%	$109.7738	$109.77	$109.75	$109.80
Purchase #6	$13.79	10.295%	$15.2097	$15.21	$15.20	$15.20
Purchase #7	$55.60	7.801%	$59.9374	$59.94	$59.95	$59.90
7 purchase totals =	$712.04		$756.3909	$756.39	$756.45	$756.40