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	$87.39	3.481%	$90.432	$90.43	$90.45	$90.40
Purchase #2	$153.86	12.477%	$173.0571	$173.06	$173.05	$173.10
Purchase #3	$101.41	5.288%	$106.7726	$106.77	$106.75	$106.80
Purchase #4	$201.34	13.203%	$227.9229	$227.92	$227.90	$227.90
Purchase #5	$140.83	9.414%	$154.0877	$154.09	$154.10	$154.10
Purchase #6	$107.29	6.260%	$114.0064	$114.01	$114.00	$114.00
Purchase #7	$137.95	10.725%	$152.7451	$152.75	$152.75	$152.70
7 purchase totals =	$930.07		$1,019.0238	$1,019.03	$1,019.00	$1,019.00