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	$139.73	13.139%	$158.0891	$158.09	$158.10	$158.10
Purchase #2	$168.99	5.868%	$178.9063	$178.91	$178.90	$178.90
Purchase #3	$209.38	3.425%	$216.5513	$216.55	$216.55	$216.60
Purchase #4	$172.41	11.713%	$192.6044	$192.60	$192.60	$192.60
Purchase #5	$102.46	6.438%	$109.0564	$109.06	$109.05	$109.10
Purchase #6	$62.38	4.585%	$65.2401	$65.24	$65.25	$65.20
Purchase #7	$163.27	9.448%	$178.6957	$178.70	$178.70	$178.70
7 purchase totals =	$1,018.62		$1,099.1433	$1,099.15	$1,099.15	$1,099.20