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	$212.49	3.233%	$219.3598	$219.36	$219.35	$219.40
Purchase #2	$50.99	5.122%	$53.6017	$53.60	$53.60	$53.60
Purchase #3	$85.53	5.401%	$90.1495	$90.15	$90.15	$90.10
Purchase #4	$175.42	9.489%	$192.0656	$192.07	$192.05	$192.10
Purchase #5	$52.73	4.823%	$55.2732	$55.27	$55.25	$55.30
Purchase #6	$151.90	4.524%	$158.772	$158.77	$158.75	$158.80
Purchase #7	$47.67	12.109%	$53.4424	$53.44	$53.45	$53.40
7 purchase totals =	$776.73		$822.6642	$822.66	$822.60	$822.70