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	$147.59	4.866%	$154.7717	$154.77	$154.75	$154.80
Purchase #2	$212.49	5.286%	$223.7222	$223.72	$223.70	$223.70
Purchase #3	$176.25	7.872%	$190.1244	$190.12	$190.10	$190.10
Purchase #4	$218.93	8.786%	$238.1652	$238.17	$238.15	$238.20
Purchase #5	$12.52	12.453%	$14.0791	$14.08	$14.10	$14.10
Purchase #6	$163.32	5.725%	$172.6701	$172.67	$172.65	$172.70
Purchase #7	$216.37	5.863%	$229.0558	$229.06	$229.05	$229.10
7 purchase totals =	$1,147.47		$1,222.5885	$1,222.59	$1,222.50	$1,222.70