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	$184.49	9.867%	$202.6936	$202.69	$202.70	$202.70
Purchase #2	$155.67	5.870%	$164.8078	$164.81	$164.80	$164.80
Purchase #3	$182.91	6.360%	$194.5431	$194.54	$194.55	$194.50
Purchase #4	$221.25	6.340%	$235.2773	$235.28	$235.30	$235.30
Purchase #5	$123.66	11.247%	$137.568	$137.57	$137.55	$137.60
Purchase #6	$59.32	4.262%	$61.8482	$61.85	$61.85	$61.80
Purchase #7	$81.55	11.205%	$90.6877	$90.69	$90.70	$90.70
7 purchase totals =	$1,008.85		$1,087.4257	$1,087.43	$1,087.45	$1,087.40