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	$6.89	9.448%	$7.541	$7.54	$7.55	$7.50
Purchase #2	$214.62	10.303%	$236.7323	$236.73	$236.75	$236.70
Purchase #3	$181.81	5.455%	$191.7277	$191.73	$191.75	$191.70
Purchase #4	$198.93	8.653%	$216.1434	$216.14	$216.15	$216.10
Purchase #5	$124.35	10.842%	$137.832	$137.83	$137.85	$137.80
Purchase #6	$140.90	8.270%	$152.5524	$152.55	$152.55	$152.60
Purchase #7	$201.72	10.341%	$222.5799	$222.58	$222.60	$222.60
7 purchase totals =	$1,069.22		$1,165.1087	$1,165.10	$1,165.20	$1,165.00